For decades, "What If?" took readers on a seemingly limitless trip through the alternate realities of the Marvel Comics Multiverse. Over two series and dozens of specials, "What If?" dealt with everything from relatively serious topics like "What If the Punisher Killed Spider-Man" to sillier fare like "What If Thor Got a Haircut." While these might seem like small changes, the worlds of "What If?" were usually filled with death, destruction and drastic changes.

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Although there haven't been any new "What If?" comics since 2015, the series has had an eerie habit of predicting the future of the Marvel Universe. Now, CBR takes a look at times when "What If?" predicted future storylines in Marvel Comics. For this list, we're looking through the history of "What If?" for stories, characters and concepts that became a big part of the Marvel Universe.

16 SPIDER-MAN IN THE FANTASTIC FOUR

What If Spider-man Joined the Fantastic Four

In 1977's "What If?" #1, Roy Thomas and Jim Craig asked "What If Spider-Man Joined the Fantastic Four?" This issue followed one of Spider-Man's earliest adventures, where he tried to join the Fantastic Four to make some much-needed cash. While the Marvel Universe Fantastic Four refused him, he joined the team in this alternate reality. Although Spider-Man found public success and celebrity as a member of the Fantastic Five, the Invisible Woman had a less prominent role on the team. She eventually left the team and moved to Atlantis, where she lived with Namor the Sub-Mariner.

Although Spider-Man has been one of the FF's closest allies since the 1960s, Peter Parker didn't officially join the team until 2011. After the Human Torch seemingly died in Jonathan Hickman and Steve Epting's "Fantastic Four" #587, the late Johnny Storm left Spider-Man his spot on the team in his will. When the FF was reorganized into the Future Foundation, Parker joined the team as a core member. Spider-Man remained a member of the group until shortly after the Human Torch's return in 2012.

15 ELEKTRA LIVES

What If Elektra Lived

Today, Elektra is famous for her multiple deaths and resurrections, but that wasn't always the case. After the assassin Bullseye stabbed her through the heart in Frank Miller and Klaus Janson's "Daredevil" #181, her death was one of the greatest tragedies in Matt Murdock's life. In 1982's "What If?" #35, Miller gave Daredevil and Elektra a considerably happier ending in "What If Elektra Had Lived?" After Bullseye dies while trying to escape prison, the Kingpin puts out a contract on Elektra for sparing Daredevil's friend Foggy Nelson. To escape the Kingpin's reach, Murdock and Elektra leave the city to start their new life together on a tropical island.

Thanks to the resurrection technology of the Hand, Elektra has never stayed dead for too long. Miller and Janson teased her resurrection in 1983's "Daredevil" #190. Miller did once more in 1990's "Elektra Lives Again," an out-of-continuity graphic novel that featured her resurrection and second death. Shortly before an alien imposter took her place, Elektra was killed and resurrected by the Hand during Mark Millar and John Romita Jr.'s 2005 run on "Wolverine."

14 BEAST AND THE THING'S NEW LOOKS

What If Beast and Thing Mutated

Two of Marvel's more monstrous heroes, the Fantastic Four's Thing and the X-Men's Beast, got their distinctive looks though scientific accidents. In 1983's "What If?" #37, both Ben Grimm and Hank McCoy continued to change in two separate tales. In Tom DeFalco and Arvell Jones' Thing story, he continued to mutate after being exposed to the biological weapon Virus X. Ultimately, the virus purged the cosmic rays from Grimm's body, transformed him into a human form and restored a nearby Alicia Masters' sight. In Alan Weiss' Beast tale, McCoy devolved into a feral state after experimenting on himself and went to live with Ka-Zar in the Savage Land.

In the Marvel Universe, both characters' looks have continued to change over time. In 1988's "Fantastic Four" #310, by Steve Englehart and Keith Pollard, the Thing temporarily gained pointy, scale-like rocks after flying through another batch of cosmic rays. In 2001's "New X-Men" #114, by Grant Morrison and Frank Quitely, the Beast's secondary mutation gave him more feline features, which he kept until his look changed again in 2013.

13 SMART HULK

What If Hulk Was Smart

Since the Hulk's debut in the 1960s, the level of his intelligence has varied quite a bit. One of the earliest looks at how a smarter Hulk might operate came in 1976's "What If?" #2, by Roy Thomas and Herb Trimpe. In that world, Banner married Betty Ross and was an accepted superhero. Without the mindless Hulk, the Avengers never formed, so Banner worked with Mr. Fantastic to cure the Thing. When Galactus showed up to eat Earth, Mr. Fantastic, Hulk and Charles Xavier combined their powers to form the X-Man, who drove Galactus away. Although this burnt out their powers, the incident turned Ben Grimm into a Hulk-like Thing.

The Hulk has gained some level of intelligence back for a moderate length of time on a fairly regular basis. After being exposed to gamma radiation in space, Banner gained control of the Hulk in 1982's "Incredible Hulk" #271, by Bill Mantlo and Sal Buscema. During Peter David's tenure as the Hulk writer in the 1980s and 1990s, the Hulk's personalities merged into a smart Hulk called the Professor. In 2014, exposure to Tony Stark's Extremis gave Hulk a new smart personality named Doc Green.

12 PUNISHER BECOMES CAPTAIN AMERICA

What If The Punisher Was Captain America

Steve Rogers and Frank Castle are two of the most seasoned combat veterans in the Marvel Universe. While their philosophies couldn't be more different, 1993's "What If?" #51 asked "What If the Punisher Became Captain America?" In Simon Furman and Paris Cullins' tale, Rogers was incapacitated while fighting the Red Skull. Shortly after his family's death, Castle took up Captain America's mantle and brutally attacked criminals. When Castle started to operate independently as the Punisher, Rogers encountered him and convinced him into becoming his permanent replacement as Captain America.

In the wake of Captain America's apparent death at the end of 2006's "Civil War," the Punisher briefly claimed to be the new Captain America. During Matt Fraction and Ariel Olivetti's 2007 run on "Punisher: War Journal," a new Hate-Monger emerged, leading his National Force in a Captain America-esque uniform. Outraged, Castle donned a costume that combined the symbolism of Captain America and the Punisher to pursue the terrorist. After that mission, the Punisher surrendered the costume to the Winter Solider, claiming that it was symbolically "too heavy" for him to wear.

11 VALERIA RICHARDS

What If Valeria Richards

In 1991, "What If?" #30 told two drastically different stories based around the survival of Mr. Fantastic and Invisible Woman's second child. In Tom DeFalco and Dale Eaglesham's version of the story, Susan Richards II slowly killed each member of the Fantastic Four by draining their life force. With help from Dr. Doom, her brother Franklin Richards eventually trapped her in the Negative Zone. In Ron Marz and Rurik Tyler's cheerier tale, Mary Richards had powerful healing abilities and became a political activist. After a failed assassination attempt, she led a revolution and ushered in a peaceful new age.

In the main Marvel Universe, Franklin Richards saved his unborn sister Valeria by sending her to an alternate reality where she was raised by Dr. Doom. After a teenage version of that Valeria aided the Fantastic Four in the Marvel Universe, Valeria was literally reborn as an infant thanks to Doom and Franklin’s powers. Since then, the young Valeria has shown a genius-level intellect that's greater than her father's and helped lead a new generation of geniuses in the Future Foundation.

10 SILK

Betty Brant as Spider-Girl in Marvel Comics

In a trio of tales by Don Glut and Rick Hoberg, 1978's "What If?" #7 asked "What If Someone Else Besides Spider-Man Had Been Bitten By the Radioactive Spider?" Despite the issue's lengthy title, three short stories looked at how Spider-Man's allies Flash Thompson, Betty Brant and John Jameson would've responded to the spider bite. As the hero Captain Spider, Thompson was killed by the Vulture, and Brant's Spider-Girl retired after inadvertently killing Uncle Ben's murderer. After becoming the jetpack-wearing hero Spider-Jameson at the urging of his father, J. Jonah Jameson, John Jameson was crushed by a falling space capsule.

Although Flash Thompson eventually became a heroic Venom and John Jameson became Man-Wolf, none of the aforementioned characters ever took Spider-Man's place. However, Peter Parker's classmate Cindy Moon was also bitten by the same radioactive spider that turned him into Spider-Man. As revealed in 2014's "Amazing Spider-Man" #4, by Dan Slott and Humberto Ramos, Moon developed powers similar to Spider-Man's abilities and was hidden away for years by Parker's mystical ally Ezekiel. After emerging from hiding, she helped Spider-Man on several adventures and starred in her own solo series.

9 AGENTS OF ATLAS

1950s Avengers

While most issues of "What If?" explicitly took place in alternate realities, it was unclear whether 1978's "What If?" #9 took place in the real Marvel Universe for decades. In that Roy Thomas and Allan Kupperberg tale, Iron Man finds a timeline where the Avengers were formed in the 1950s. In the issue, secret agent Jimmy Woo recruited the old Marvel characters Gorilla-Man, Venus, Marvel Boy, Human Rocket and the new hero 3-D Man to form a precursor to the Avengers. After defeating the villain Yellow Claw and saving President Dwight Eisenhower, the group was ordered to disband.

In the 1998 miniseries "Avengers Forever," by Kurt Busiek, Roger Stern, Carlos Pacheco and Jesus Merino, the 1950s Avengers popped up again. Shortly after their world was revealed as an alternate reality, it was destroyed by the time-traveling villain Immortus. In 2006, Jeff Parker and Leonard Kirk reunited the team, without 3-D Man, in "Agents of Atlas." That series revealed that the team had operated in the 1950s and reunited them in the modern Marvel Universe for four years of new adventures.

8 DR. DOOM'S REFORM

What If Dr Doom Was A Hero

Even though Dr. Doom is one of the defining villains of the Marvel Universe, his complex code of honor has made him act like a hero more than once. In 1980's "What If?" #22, Don Glut and Fred Kida asked "What If Dr. Doom Had Become a Hero?" In this tale, Doom was never scarred by one of his experiments since he took Mr. Fantastic's scientific advice. Doom became a hero, rescued his mother's soul from Mephisto and married his love Valeria. After Doom took over Latveria, Mephisto attacked the country and forced Doom to give him Valeria as revenge for his mother's freedom.

In 2015, Dr. Doom helped save the multiverse by combining parallel worlds together in "Secret Wars." Unsatisfied with his limitless power in that world, Doom started helping Iron Man in the Marvel Universe. After 2016's "Civil War II" left Tony Stark comatose, the reformed Doom has donned a new suit of armor as the star of Brian Michael Bendis and Alex Maleev's ongoing series "Infamous Iron Man. "

7 SPIDER-MAN'S CLONE LIVES

What If Spider-Man's Clone Lived

Like Spider-Man's infamous "Clone Saga" of the 1990s, 1981's "What If?" #30 has its roots in the original "Clone Saga." While Spider-Man's clone seemingly died in that 1970s story, Bill Flanagan and Rich Buckler wondered "What If Spider-Man's Clone Lived?" In that alternate reality, Spider-Man's clone survives a final confrontation with the Jackal and puts Peter Parker in suspended animation. After trying to resume Parker's life, he realizes that he's a clone and releases Parker. After the pair teamed up to beat the Kingpin, they decided to share a life together as brothers.

In the main Marvel Universe, Spider-Man's clone, Ben Reilly, survived the original "Clone Saga" and led a nomadic life for years. In 1994's "Web of Spider-Man" #118, by Terry Kavanagh and Steven Butler, Reilly debuted as the Scarlet Spider. After working closely with Peter Parker, Reilly assumed Spider-Man's identity when Parker briefly retired. Although Reilly died in 1996, another Spider-Man clone, Kaine, became a new Scarlet Spider in 2012. Earlier this year, Reilly returned to life in Dan Slott and Jim Cheung's "The Clone Conspiracy: Dead No More" and is set to star in the upcoming "Ben Reilly: The Scarlet Spider."

6 WOLVERINE: AGENT OF S.H.I.E.L.D.

What If Wolverine Was An Agent of SHIELD

While the second volume of "What If?" ended with some shockingly downbeat stories in the late 1990s, it began with some decidedly happier adventures. In 1989's "What If?" #7, future Image Comics founders Jim Valentino and Rob Liefeld asked "What If Wolverine Was an Agent of S.H.I.E.L.D.?" In that world, Wolverine took jobs for Nick Fury after leaving Canada's Department H. After working with Black Widow to purge Hydra's sleeper agents from S.H.I.E.L.D., Wolverine joined up as an agent, instead of the X-Men. After one of the last vestiges of Hydra killed Nick Fury, Wolverine became Director of S.H.I.E.L.D., shut down the revived Sentinel program, defeated the Mutant Registration Act and helped mutants gain widespread acceptance.

Although Wolverine never fully joined S.H.I.E.L.D., Logan has worked with both Nick Fury and S.H.I.E.L.D. fairly consistently. After being brainwashed by Hydra, Wolverine killed almost 400 S.H.I.E.L.D. agents in 2004's "Wolverine" #20, by Mark Millar and John Romita Jr. In the follow-up story arc, "Wolverine: Agent of S.H.I.E.L.D.," a deprogrammed Wolverine led S.H.I.E.L.D.'s efforts to take down Hydra and the Hand. A few months later, Logan worked as a S.H.I.E.L.D. asset again in the alternate timeline "House of M."

5 SPIDER-GIRL

Spider-Girl

The worlds from most of "What If?" don't last much longer than a single issue, but "What If?" #105 inspired an entire publishing imprint. In that 1998 story, Tom DeFalco and Ron Frenz created May "Mayday" Parker, the super-powered teenage daughter of Spider-Man and Mary Jane. After the Green Goblin's grandson Normie Osborn tried to lure Peter Parker out of retirement, Mayday learned about her father's heroic past. After discovering her own spider abilities, she donned Ben Reilly's old Spider-Man costume and defeated Normie as the new Spider-Girl.

After that issue's runaway success, Spider-Girl received her own series later in 1998. As part of the MC2 line, the series followed the children of today's heroes in a fairly optimistic future. Although "Spider-Girl" was only supposed to last for 12 issues, the title continued for 100 uninterrupted issues before being relaunched in 2006. Long after the rest of the MC2 line folded, "Spider-Girl: The End" concluded her solo adventures in 2010. Since then, Spider-Girl has occasionally popped up in alternate reality crossovers, like 2014's "Spider-Verse."

4 PLANET HULK

What If Hulk Was A Barbarian

In the 1970s, the Hulk was briefly married to Jarella, a green-skinned queen from the sub-atomic planet K'ai. While she died in the Marvel Universe, Peter Gillis and Herb Trimpe looked at what could've happened if she had lived in "What If the Hulk Had Become a Barbarian?" In 1980's "What If?" #23, Hank Pym sends the Hulk and Jarella back to K'ai permanently. When the Dark Gods and their horde of undead warriors attacked the microscopic world, the Hulk and Jarella assembled Kai's greatest defenders. After pushing the threat back, the Hulk vowed to continue to protect his newly-adopted home.

In 2006, Greg Pak, Carlo Pagulayan and Aaron Lopresti revisited several aspects of this story in the modern classic "Planet Hulk." After being exiled in space, the Hulk crashed on the planet Sakaar, where he was forced to fight in gladiatorial combat. Hulk formed the Warbound with his fellow gladiators and conquered the barbaric world. After the Hulk's brief marriage to the alien Caiera, the Hulk and his Warbound traveled to Earth in 2007's "World War Hulk."

3 ONE MORE DAY

What If Spider-Man Never Married Mary Jane

Spider-Man and Mary Jane are one of the most recognizable couples in superhero comics. While they got married in 1987, Danny Fingeroth and Jim Valentino asked "What If Spider-Man Had Not Married Mary Jane?" in 1990's "What If?" #20. After becoming concerned for Mary Jane's safety, Peter Parker left her at the altar and began to work for the mercenary Silver Sable. As Spider-Man, he began to date the Black Cat, Felicia Hardy, and eventually married her. After Hardy died in battle, Parker started a romantic relationship with Silver Sable.

In one of the most infamous storylines in the past decade, Spider-Man and Mary Jane were unwed in 2007's "One More Day." In J. Michael Straczynski and Joe Quesada's tale, Spider-Man and Mary Jane agreed to give their marriage to Mephisto in exchange for Aunt May's life. While May's life was saved, their marriage was written out of continuity. While this has been the status quo for 10 years, "Amazing Spider-Man: Renew Your Vows" has recently explored an alternate reality where the couple's marriage survived.

2 RED HULK

What If Thunderbolt Ross Was Hulk

One of the more revisited "What If?" premises revolved around the idea of other people becoming the Hulk. In the 2005 special "What If General Ross Had Become the Hulk?," Peter David and Pat Olliffe looked at a world where the Bruce Banner's fiercest opponent took his place. After being bombarded by gamma rays, Ross turned into a gray, mustached Hulk and accidentally killed a teenage Rick Jones. While he was being pursued by the military, this Hulk accidentally killed his daughter Betty Ross by throwing a tank into her home. Devastated by his actions, Ross returned to human form and was executed at point blank range by a grieving Banner.

Just three years later, General Ross became the Red Hulk in 2008. In 2008's "Hulk" #1, by Jeph Loeb and Ed McGuinness, the mysterious, intelligent Red Hulk debuted while carving an endless path of destruction. While the Red Hulk's identity was initially a mystery, it was eventually revealed that Ross turned himself into the beast with siphoned radiation from the Hulk and others. Since then, the Red Hulk has been an Avenger and anti-hero around the Marvel Universe, though Ross' version has since been depowered.

1 JANE FOSTER THOR

What If Jane Foster Was Thor

While the Odinson has been reduced to the "Unworthy Thor" in the modern Marvel Universe, Jane Foster has taken his place as Thor. While this has divided readers, Foster wielded the mighty Mjolnir for the first time in 1978's "What If?" #10. In that alternate reality tale by Don Glut and John Buscema, Foster found the hammer and called herself Thordis. After saving Thor, who had been turned into the mortal Don Blake, Thordis saved Asgard from Ragnarok. Although Foster was compelled to surrender the hammer to Thor, she married Odin and became the Queen of Asgard.

After the Odinson was deemed unworthy of wielding Mjolnir in 2014's "Original Sin," Jane Foster became the new Thor in 2014's "Thor" #1, by Jason Aaron and Russell Dauterman. Since then, Jane's Thor has fought the Serpent Cul, Silver Samurai and the Roxxon Corporation. She has also taken Thor's place on the Avengers and has shown a level of control with Mjolnir that no previous incarnation of Thor has ever exhibited. Jane's Thor and the classic Thor Odinson seem set to encounter one another in the upcoming crossover "Generations."

What if your favorite "What If?" that came true, but wasn't on this list? Let us know in the comments!