Time travel is an oft-repeated science fiction trope that has been used numerous times in multiple stories, with each new take offering a new way at looking at the world around us through the past, present, and the future. Our love of movies like Back to the Future and The Terminator and the time travel dilemmas they present are so successful because they are rooted in humanity's inherent wonder about what's next? What will happen in the future, what will we be like in 20 years?  What will the world be like? These are all questions that have been asked through science fiction over the years, with many comic storylines also being influenced by our wonder of the future. Marvel's Days of Future Past and DC's Kingdom Come are both iconic examples of the Big Two's forays into future timelines, but really just scratch the surface when it comes to some of the older versions of our favorite characters that we've seen explored.

Most recently, Marvel has developed a possible future known as the Wastelands, which was created by Mark Millar and Steve McNiven. The original Old Man Logan mini-series took place in the near future of the Marvel Universe and featured a very different look at the mutant once known as Wolverine. Old Man Logan turned the deadliest weapon on Earth into a family man at the end of the world, and Old Man Hawkeye has explored that particular future timeline further with an aged blind version of the Avenger. These two characters are not the first older versions that have appeared over the years and they certainly won't be the last, considering the ongoing popularity of the Old Man series. Even DC has joined in on the fun recently with Old Lady Harley, which features an old Harley Quinn in a post-apocalyptic future. So what could be next for Marvel's Old Man franchise? And what other old version have we already seen? Let's find out...

20 WANT: BLADE

First of all, we're kind of surprised we haven't seen Old Man Blade already. As a human-vampire hybrid, Eric Brooks AKA Blade has spent many years fighting the eternal threat of vampires. While his hybrid physiology doesn't make him immortal like his nocturnal brethren, he does age at a very reduced rate.

Any look at his future self will be forever tied with his ongoing battle against the vampire army, and given the post-apocalyptic nature of most Old Man-type stories, it probably wouldn't go well for the human race. Old Hunter Blade could very well be fighting his fight until he's the very last human on a desolated world of vampires, which is a story we'd like to see.

19 BEEN DONE: HULK

Hulk's older persona Maestro first appeared in Peter David and George Pérez' Future Imperfect, which introduced readers to a new world set 100 years after the present Marvel Universe (circa 1993). Following a nuclear world war that killed the superheroes, the Hulk is left driven insane by his absorption of the radiation that pushed humanity to the edge of extinction.

He is stronger than present Hulk due to the increase in radiation levels, possesses the intellect of Bruce Banner coupled with a few of the Hulk's less desirable personality traits, making him a very dangerous foe. Maestro has since moved from the Future Imperfect timeline to the mainstream Marvel universe for events like Secret Wars and recent appearances in the Old Man Logan ongoing.

18 WANT: CAPTAIN MARVEL

We've already seen teases of a post-apocalyptic version of Carol in recent solicitations for her new solo series, which revealed designs for Captain Marvel and her new crew (Spider-Woman, Echo, and Hazmat) trapped on an exiled island, so the older version of the character should follow a different path.

Thankfully Captain Marvel's half-Kree physiology gives her a connection to the Marvel Cosmic universe that has remained a constant in her life, including her time spent as the overpowered Binary during the Claremont era of Uncanny X-Men. While the character of Captain Marvel has become one of the most powerful heroes of Earth in her current form, we would love to see a Binary-powered Carol protecting the galaxy with years of experience behind her.

17 BEEN DONE: MS. MARVEL

There have been two distinct older versions of Kamala Khan, the latest hero to take the name, Ms. Marvel. During the "Old Woman Laura" storyline in Wolverine, Kamala appears as the President of the United States, which would be a great ending for the character. However, in the pages of the latest volume of Exiles, we were introduced to a new post-apocalyptic version of the character who was known as Khan.

During her short time with the Exiles, it is revealed that Khan has lost her family as well as her city of New Jersey, leading to a very different version of the character than fans were used to seeing. Khan sacrificed herself to save her new teammates from a Galactus-powered villain known as the Time-Eater.

16 WANT: DAREDEVIL

You don't have to look too far in the Marvel Multiverse to find a number of alternate versions of Matt Murdock, both present-day versions and older. And it's all too easy to imagine Murdock following in the footsteps of his teacher before him, becoming his own version of Stick to the youths of Hell's Kitchen.

But to really take the Old Man theme and run with it,  we want to see the return of former Daredevil scribe Frank Miller, who was also responsible for DC's iconic The Dark Knight Returns miniseries. Give Old Devil Murdock the Dark Knight Returns treatment from the glory days Frank Miller and tell the tale of an old and defeated Devil of Hell's Kitchen still fighting for his neighborhood.

15 BEEN DONE: SPIDER-MAN

Spider-Man Reign the Spider-Man costume ripping apart.

2006 saw the release of Kaare Andrews four-issue Spider-Man: Reign, which was set 30 years in the future. Peter Parker is in his 70s, and is a shell of his former self, living in an authoritarian New York City under the control of a police force known as the Reign. Parker works as a florist and retired as Spider-Man years ago following the heartbreaking loss of his wife Mary-Jane, due to exposure to his irradiated DNA.

When the Mayor of New York takes complete control of the city and traps the citizens within a force-shield known as the WEBB, Parker is forced to come out of retirement one last time to save his city as he battles against a reassembled Sinister Six and the Reign.

14 WANT: SCARLET WITCH

Wanda Maximoff is a roller-coaster ride of a character, as a villain-turned-hero-turned-villain-turned-hero who has been responsible for both the near-extinction of the mutant race as well as the repopulation of the mutant race. So to imagine all the different catastrophes the Marvel Universe would have gone through to get to Old Witch Wanda is kind of frightening.

Wanda has constantly dealt with issues that would shatter the sanest of people, and her upbringing and the various manipulations and troubled relationships across her career haven't always left her in the best mental state. This doesn't leave a lot of positive hope for an older Wanda, especially considering the usual end of the world scenarios that feature in these types of stories.

13 BEEN DONE: MISTER FANTASTIC

If we're talking about the mainstream Reed Richards, the chances of his older self doing great things for the Marvel Universe are very good. Unfortunately, the Ultimate universe version of Reed Richards took things to the next level following an evil turn that united his universe of heroes against him.

Richards, who had become immortal due to his powers, spent 1000 years in the distant future expanding his knowledge and abilities, where he created an army of genetically engineered superhumans known as the Children of Tomorrow. He became known as Maker and actually managed to survive the destruction of the Ultimate universe., remaining a thorn in the side of the mainstream universe's heroes.

12 WANT: BLACK PANTHER

Black Panther is a character who is steeped in legacy and traditions, with the title of both King and Black Panther being passed down among the generations. T'Challa's inevitable future is that of future monarch of Wakanda, raising the next generation in his footsteps like his father, and his father before him.

What's really interesting is what kind of world that character would exist alongside. Is Wakanda the sole surviving country following a devastating extinction event? Or has King T'Challa evolved past Wakanda's borders to become the leader of the free world? The possibilities truly are endless when it comes to a character with a rich legacy like the Black Panther.

11 BEEN DONE: THOR

Old King Thor is not the first older version of Thor that we've seen, but he is the most developed. He first appeared in Jason Aaron's 2012 run on Thor, which also featured stories of a younger Thor as well as the present-day version. King Thor exists in the far future as the All-Father of Asgard. He has finally ascended to his father Odin's position and possesses the Odin/Thor Force, although it came at a heavy cost.

King Thor rules over an empty Asgard and visits a dead Earth, both lost due to his failures against Gorr the God Butcher and Loki, respectively. He is accompanied by his three granddaughters who help him finally defeat Gorr, and restart life on Earth in a rebooted Adam and Eve (Jane and Steve) tale.

10 WANT: NOVA

We've watched Richard Rider grow up over the years, from his time as Kid Nova with the New Warriors to his role as a defender of the cosmos alongside characters like the Guardians of the Galaxy. And while we wanted to see a more cosmic outing for an older Captain Marvel, with Rich it might be time for the Human Rocket to come home. After rebuilding the Nova Corps and fighting in numerous galactic wars, maybe it's time for a happy ending.

He definitely stepped up to the daunting task that was left him when the Nova Corps was initially destroyed, and after facing Annihilation and the Cancerverse, he's earned the life of a retired family man, dreaming of his past adventures as the last Nova.

9 BEEN DONE: RACHEL SUMMERS

One of the most iconic X-storylines is "Days of Future Past," which introduced Rachel Summers, future daughter of Scott Summers and Jean Grey. Rachel eventually joined the present day X-Men and continued her adventures there, before joining the British off-shoot Excalibur.

Rachel sacrificed herself for her teammate Captain Britain and was trapped 2000 years in the future, where she gathered a group of rebels who became known as the Askani to fight Apocalypse. She then became known as Mother Askani and eventually was responsible for saving her younger brother Nathan's life by bringing him into the future as well, where he could grow up to become the militaristic mutant known as Cable.

8 WANT: MYSTIQUE

Raven Darkholme has a very unique powerset that opens up quite a few possibilities when discussing older versions of characters. With her shape-changing abilities, she is able to hide her true age and is suspected as being at least as old as Wolverine. While Logan's healing factor eventually slows on him and his aging increases, Mystique's abilities may even extend her lifespan past the Canucklehead.

She's already spent a century amassing a fortune, and contacts around the world to further her plans, what could another century add to that. And another century after that? But the real question a series like that would answer is what would that many years do to a person like Mystique?

7 BEEN DONE: FRANKLIN RICHARDS

Franklin Richards is the mutant son of Reed and Sue Richards, who is fated to become one of the most powerful mutants around with extreme reality-manipulating and psionic abilities. A version of his older self was first seen alongside Rachel Summers in the "Days of Future Past" storyline, though his powers were dampened.

But at some point in time during Franklin's youth, he was abducted by his grandfather Nathaniel Richards and raised outside time, growing into the teenager known as Psi-Lord. He wore specially designed armor that drained his abilities so he could maintain control and founded a group known as the Fantastic Force, before fixing the timeline and erasing him (and his and Rachel's power-mad son Hyperstorm) from existence.

6 WANT: LUKE CAGE

Luke Cage is a character we don't see too many older versions of, which seems surprising. There are numerous alternate reality versions of the character, but his daughter Danielle Cage is represented more in the future than he is. We want to see a wisened Old Man Cage still watching over Harlem after all of his years as a superhero, doing it only the way he can.

Sure, we love Dani's evolution into Captain America, but we still want to see Grandpa Cage solving problems and teaching lessons around his neighborhood. It may not sound as epically heroic as some of the Old Man stories we've seen, but Cage's greatest strength has never been his powers, and that would showcase his legacy best.

5 BEEN DONE: JEAN GREY

For a very long time, the thought of an older Jean Grey seemed like nothing more than wishful thinking, as the character had been dead in the Marvel Universe for years. Recently, a new younger Jean Grey was brought to the present day timeline along with the rest of the time-displaced Original Five members (the X-Men do so love to play around with the timelines).

During the "Battle of the Atom" event, a new Brotherhood from the future arrives in the present, with a new female Xorn on the team. This version of the character (which is technically the third Xorn) is soon revealed to be the grown-up version of young Jean, who had become obsessed with sending the young X-Men back to the past, at all costs.

4 WANT: BLACK WIDOW

Natasha Romanova is another character who is older than she appears and could have a long future ahead of her, thanks to biotechnology enhancements she had received during her time as a Russian spy. But how that future develops is the real question, as Black Widow has followed a number of different paths over the years.

Given her history, she could become the world's top spy à la Nick Fury, or a dark side could develop and Natasha could become the next leader of Hydra. And considering that Black Widow is currently dead after the events of Secret Empire and has been replaced by a clone with her memories, anything is really possible in her future.

3 BEEN DONE: CAPTAIN AMERICA

Captain America kind of exists as his own future self, though we have seen aged versions of Steve Rogers before. The most memorable version of the Sentinel of Liberty comes from Alex Ross' Earth-X trilogy, which presented one of the most unique representations of an older Cap we've ever seen. At 100 years old, Cap still fights alongside a new generation of heroes and villains in a world that has been mutated by Terrigen Mists.

Over the course of the trilogy (Earth-X, Universe X, and Paradise-X) Cap manages to defeat a new threat known as the Skull alongside his surviving allies, help raise a new savior in the reincarnated form of Mar-Vell, and ultimately become an avenging angel of paradise. Not bad for a skinny kid from Brooklyn.

2 WANT: GROOT

Groot started his comic life as a Marvel monster but has developed into a fan-favorite member of the Guardians of the Galaxy. While it would definitely be interesting to see a return to the Groot of old as a giant monster in his later years, there is another interesting concept for the Flora colossus.

Considering he was previously exiled from his homeworld of Planet X due to his love of the mammalian creatures that maintained his world, we see Old Tree Groot as an aged protector of the furry folk. With his ability to grow and regenerate his body, Old Tree Groot could become Old Forest Groot, and maybe even Planet Groot one day.

1 BEEN DONE: KANG

The original Old Man story revolves around one of the Avengers deadliest foes. Kang the Conqueror is a time-traveler who sets his sights on defeating the Avengers, using highly advanced future technology to battle the heroes. While Kang is set on conquering timelines, the character of Immortus is tasked with preserving the timelines. Immortus is actually the future self of Kang, who has renounced his former conquering ways, much to the chagrin of his former self.

The two are constantly at odds with each other, though Immortus has also worked against the Avengers many times as well. Fun fact, Immortus is actually Nathaniel Richards, father of Reed Richards, and has gone by other aliases like Iron Lad, Rama Tut, and the Scarlet Centurion over the years.