To the reader, comic book superheroes are immortal. To the heroes themselves, deadly dangers lurk around every corner. That is in spite of comicdom's sliding timescale, which allows characters who have been around for the better part of a century to remain as youthful and energetic as ever. But every now and again, time catches up to one of our heroes. They either get too old to be running around in spandex, or they decide they want to spend more time with their loved ones, or they fall heroically in battle. Odds are they will be back within the year, but what to do in the meantime? Can't let the legacy fade away, or worse, fall into the wrong hands.

To that end, superheroes will often train a younger sidekick or successor to take over for them when they retire or they perish. In other cases, a superhero replacement is not so carefully chosen. Some replacements were simply so inspired by a fallen hero's accomplishments that they take on a legacy name of their own volition. Regardless of how a character becomes a replacement hero, they have a lot to live up to, and not all of them can hack it. The quality and longevity of replacement superheroes has varied tremendously. Some do so well that they utterly eclipse their namesakes. Others mess up so badly that their predecessor comes back just to beat them up. We've got ten of the best -- and ten of the worst -- examples of replacement heroes listed below.

20 BETTER: RIRI WILLIAMS AS IRONHEART

riri williams aka ironheart in marvel comics

At the end of "Civil War II," Tony Stark was seemingly ended by Captain Marvel. The last time Tony was out of commission, his best friend, James Rhodes, became Iron Man until Tony could return. This time, Tony's replacement was a 15-year-old whiz kid named Riri Williams.

Riri has proven just as adept at operating the Iron Man armor as anyone who came before her. She even joined the Champions, which consisted of many of Marvel's greatest young heroes, including Ms. Marvel and Spider-Man. Best of all, unlike Tony, Riri didn't have years of questionable moral decisions hanging over her.

19 WORSE: JASON TODD AS ROBIN

Jason Todd as Red Hood

After Dick Grayson, the original Robin, grew up and took the codename Nightwing, Batman found himself at loose ends. He missed having a sidekick to patrol with and Jason Todd seemed like the perfect solution to his loneliness. Also an orphan, Jason needed a new home anyway, and training to be Robin would give him a new purpose in life.

Unfortunately, Jason proved far more volatile than his predecessor. He had a bad temper and soon began treating criminals far too harshly. But in the end, Jason's infamous demise wasn't due to anything he did. Rather, his own mother sold him out to the Joker. Both she and Jason paid for her betrayal with their lives.

18 BETTER: MILES MORALES AS SPIDER-MAN

Miles Morales Spider-Man

In the Ultimates Universe, Peter Parker had been Spider-Man for years, just like in the main Marvel Universe. He defended New York with honor until finally, one day, too much happened too fast. Gravely injured, Peter used the last of his strength to save Mary Jane from Norman Osborn then passed away in her arms.

Enter Miles Morales. Miles had recently gained spider powers but was initially too afraid to do anything with them. After Spider-Man's demise, a guilt-ridden Miles finally found the courage to don a spider suit of his own. He has since joined the Marvel Universe proper, where he became an Avenger and, later, a member of the Champions.

17 WORSE: AMADEUS CHO AS THE HULK

amadeus-cho

Amadeus Cho's main appeal as the Hulk was his ability to retain his intelligence and equanimity even after transforming. While Bruce Banner has occasionally been able to combine the Hulk's brawn with Dr. Banner's brain, he's most famous for going on mindless rampages. Amadeus was a refreshing departure from that archetype.

Unfortunately, Amadeus lost that control real quick. It got so bad that his friends had to inject him with gamma-absorbing nanobots to eliminate the gamma radiation from his system. Currently, Amadeus retains a small portion of his Hulk powers. It's just enough to allow him to transform into a smaller version of the Hulk without costing him his marbles.

16 BETTER: KAMALA KHAN AS MS. MARVEL

Ms Marvel Kamala Khan

Carol Danvers became the first Ms. Marvel in 1977, as a way to carry on the legacy of Captain Marvel. She became the face of the Marvel family and served as an inspiration to girls in both the Marvel Universe and the real world. Kamala Khan was one of those girls.

Kamala, an Inhuman teen from New Jersey, loved Carol Danvers so much that she patterned her entire superheroic career after hers. And yet Kamala has bravely forged her own path, learning to respect herself as much as she respects her heroes. Kamala's tenacity and vulnerability have made her one of the most popular new Marvel characters of the last decade.

15 WORSE: CHARLEY PARKER AS HAWKMAN

Charley Parker as Golden Eagle

Even before taking on the mantle of Hawkman, Charley Parker wasn't exactly an A-list hero. Calling himself Golden Eagle, he hung around with the Teen Titans for a while. But Charley's desire to be a hero was nowhere near as strong as his desire to get revenge on Hawkman and Hawkgirl for daring to not live up to his expectations.

Charley, in a surprising twist given his previous slacker tendencies, concocted an elaborate scheme to get Hawkman out of the picture. Charley himself then took over as Hawkman and tried to force Hawkgirl to go back to Thanagar with him. Luckily for everyone, the original Hawkman returned in time to teach him a lesson... with his fists.

14 BETTER: DINAH LANCE AS BLACK CANARY

Black Canary in Birds of Prey

The original Black Canary, Dinah Drake, was a revered member of the Justice Society of America. Relying only on her wits and fists, Dinah helped to put away criminals of all sorts, from petty crooks to indestructible cosmic entities.

Cut to years later, when Dinah Drake got married and had a daughter, Dinah Lance. Drake resolutely did not want her daughter following in her footsteps. Lance, of course, wanted nothing more than to be a hero and became the new Black Canary. Not only has she led the Justice League, she also has the famous Canary Cry that is now indelibly associated with the character.

13 WORSE: KON-EL AS SUPERMAN

superboy

There have been quite a few Superboys over the years. The original was, of course, Clark Kent himself, who cut his teeth as Smallville's teen defender. Much later, long after he'd become Superman, Clark lost a fight with the alien Doomsday and succumbed to his injuries. But those in charge had foreseen the possibility of Superman falling in battle and thoughtfully created a clone to replace him.

That clone was Kon-El, aka Mr. Don't Ever Call Me Superboy. His creators gave him the mind of a teenager, and it showed. Kon-El was much more of a gloryhound than Kal-El ever was. It wasn't until an innocent civilian was killed on his watch that he got his head in the game.

12 BETTER: JAIME REYES AS BLUE BEETLE

Jaime Reyes as Blue Beetle

The Blue Beetle is one of the few legacy heroes who exponentially improves with each successive generation. Blue Beetle I, Dan Garret, was pretty much your standard superhero. Blue Beetle II, Ted Kord, brought unprecedented humor and inventiveness to the role. Both did admirable work, but neither can measure up to Blue Beetle III.

Jaime Reyes, a teenager from Texas, found the Scarab that had inspired his predecessors' heroism. The Scarab bonded with Jaime, granting him access to a sweet alien suit of armor. And yet, Jaime's greatest dream is still to become a dentist so he can put his kid sister through college.

11 WORSE: BUCKY BARNES AS CAPTAIN AMERICA

Bucky Barnes as Captain America

Once upon a time, Bucky would have been the natural choice to succeed Steve Rogers as the Sentinel of Liberty. But years of brainwashing took its toll on his personality and mental health. Everyone, from civilians to government officials, knew Bucky wasn't suited to be Captain America. Everyone, that is, except Tony Stark, who gave him the shield anyway.

During "Fear Itself", Bucky was seemingly ended in inglorious fashion by the Red Skull's daughter, Sin. He was revived by Nick Fury, but rather than let everyone know he was still alive, Bucky decided he didn't feel worthy of being Cap anymore and straight-up disappeared.

10 BETTER: WALLY WEST AS THE FLASH

The Flash Rebirth Wally West

If a hero sticks around long enough, they are almost guaranteed to spend a few years gone for story purposes. Barry Allen's time came during Crisis on Infinite Earths, when he gave his life to preserve the universe. Naturally, Barry's nephew, Wally West, was devastated. But the fans quickly got over Barry's demise, thanks to Wally's stellar turn as the Fastest Man Alive.

Wally West had spent years as his uncle's loyal sidekick and as a founding member of the Teen Titans. All that experience paid off when it came time for him to finally fly solo. Although not always as quick in his mind as he is on his feet, Wally has truly done Barry's legacy proud.

9 WORSE: DANE WHITMAN AS BLACK KNIGHT

Nathan Garrett used the ancient Black Knight armor and sword to commit crimes. After being critically injured in a fight, Nathan told his nephew, Dane Whitman, the truth about himself. Dane in turn decided to become a new, more heroic Black Knight.

That sounds very impressive, and compared to his dearly departed Uncle Nathan, Dane is practically a saint. But when compared to previous Black Knights, Dane is a little lacking. He has a tendency to get captured, brainwashed, turned to stone, and so on. Meanwhile, what was his distant ancestor and original Black Knight, Sir Percy of Scandia, doing? Defending King Arthur himself, that's what.

8 BETTER: COURTNEY WHITMORE AS STARGIRL

Courtney Whitmore as Stargirl

Multiple heroes have gone by the name Starman, but there has only been one Stargirl: Courtney Whitmore. Originally, she called herself the Star-Spangled Kid, after another hero of that name. But then she inherited the Cosmic Staff from Jack Knight, a previous Starman, upon his retirement.

The Staff allows her to fly and shoot energy beams -- it's extremely powerful, but Courtney wielded it like a pro right from the start. She hasn't even graduated high school yet, but Stargirl is more than capable of playing with the big kids. She has served with the Justice Society and the Justice League.

7 WORSE: TORO AS THE HUMAN TORCH

Thomas Raymond, aka Toro, was one of the first teen sidekicks. Fighting crime alongside the original Human Torch and the Young Commandos, Toro used his natural immunity to fire to fight oppressive forces. But after the Human Torch seemingly exploded, Toro retired.

Years later, the Mad Thinker captured Toro and used an electroshock collar to force Toro into working for him. Believing himself to be the Human Torch, Toro attacked the Sub-Mariner. The collar was damaged in the fight, allowing Toro to make a fatal attempt at getting revenge on the Mad Thinker. He got better, but he notably stayed away from calling himself the Human Torch from then on.

6 BETTER: NADIA PYM AS WASP

Wasp, Nadia Pym

Nadia Pym, daughter of the original Ant-Man, was taken away to the Red Room as soon as she was born. Even as her captors encouraged her to become a brilliant scientist like her father, Nadia plotted her escape. She acquired some Pym Particles and busted herself loose.

Nadia then made her way to America, where she sought out her father. Hank Pym was, sadly, believed deceased at the time. Nadia instead met up with Janet van Dyne, the original Wasp, who gave her permission to call herself the Wasp too. Nadia still has a lot to learn about the real world, but she is already shaping up to be at least as winsome and wonderful as her predecessor.

5 WORSE: TEEN TONY STARK AS IRON MAN

After Iron Man went rogue during "The Crossing," his teammates sought help from a younger Tony Stark from the past. The gambit worked -- the sight of his younger self caused Iron Man to repent and sacrifice himself to make up for his misdeeds. That would have left the world without an Iron Man, but Teen Tony was still around. Who better to take over for Tony Stark than Tony Stark?

As it turns out, anyone else would have been better. Like many ideas from the '90s, Teen Tony didn't have much long-term appeal. He ended up merged with the regular Tony to form a new improved Tony. This is the Tony currently running around the Marvel Universe.

4 BETTER: CONNOR HAWKE AS GREEN ARROW

In the mid-'90s, Green Arrow appeared to fall victim to an attack in Metropolis. But unbeknownst to Ollie, just before he perished, he'd found the perfect successor: his long-lost son Connor Hawke, who had spent his teen years in a California monastery learning patience and archery.

Once Ollie "passed away" Connor struggled to use his training to pick up where his father left off. Despite his doubts, Connor proved an excellent Green Arrow. He became one of the few to survive an encounter with the assassin Lady Shiva. He even received the endorsement of Ollie's ex, Black Canary, who gifted him one of Ollie's bows.

3 WORSE: LORENA MARQUEZ AS AQUAGIRL

The original Aquagirl, usually just called Tula, fought alongside Aqualad and the Teen Titans for decades. She was never a heavy hitter, and she suffocated in toxic water in Crisis on Infinite Earths. Still, Tula was a solid heroine with a solid record of teaching crooks a lesson.

The same cannot yet be said of Lorena Marquez, a human teen who suddenly gained the ability to breathe underwater after San Diego slid into the ocean. Lorena has the potential to be great; as seen in a possible future, she may one day develop telepathy, just like her predecessor had. But as of now, it seems like Lorena's best, most powerful days are still ahead of her.

2 BETTER: KATE BISHOP AS HAWKEYE

Hawkeye Kate Bishop

While the original Hawkeye, Clint Barton, was busy being gone, Kate Bishop took it upon herself to protect New York City in his name. Throwing together a costume from bits and bobs originally belonging to Hawkeye and Mockingbird, Kate joined the Young Avengers to save the world from Kang the Conqueror.

After the danger passed, Kate decided she liked being a hero and kept at it. Even after Clint was resurrected, she continued to fight crime as Hawkeye. The two Hawkeyes bonded over their shared love of shooting things with pointy sticks and have since become an inseparable, unbeatable duo.

1 WORSE: CHARLIE GAGE-RADCLIFFE AS BATGIRL

Most replacement heroes get permission from their predecessors before taking over their name, or at least wait until their predecessor is deceased before jumping into the fray. But not teleporting teen Charlie Gage-Radcliffe! She called herself Batgirl and swung into action without the blessing of any prior Batgirls, not even Barbara Gordon, who was now Oracle.

Barbara, both angry and afraid for Charlie's safety, gave the newbie what-for. Chastised, Charlie agreed to give up the Batgirl title, though she stopped short of promising to give up crime-fighting all together. She later found her place in the Birds of Prey as, ironically, Misfit.