Sidekick Graduations Stick

In Super Hero Comic Books, the Status Quo Is God. It might not seem like that at first, what with all the deaths, resurrections, Face Heel Turns, Heel Face Turns, and whatnot. It's a rare year -- honestly, a rare month -- where comic book readers aren't gravely informed that Nothing Is the Same Anymore.

Yet, take a look at the major characters of The DCU or the Marvel Universe today and five or ten years ago. Things will be different, but not that different, and most of the major changes will seem to have happened recently. The companies that own these characters, like all large corporations, are conservative, and all these dramatic changes have a noticeable tendency to cancel out in the long run. Once a character establishes an iconic status quo, or becomes part of another character's iconic status quo, it can be extremely difficult to change anything major about that character.

There is, however, one category of change that's an interesting exception: the "graduation" of sidekicks to become independent heroes in their own right, or assume their mentor's mantle. Perhaps it is only because this tends to be accompanied by finally aging the character from a teen to an adult, and even in the Ret Con-happy world of comics, reversing that without breaking the Willing Suspension Of Disbelief is hard.

Still, it also seems that negative fan reaction to these changes is also much, much rarer than with the average change. What little of it there is tends to occur when another character's mantle is taken by the graduating sidekick, with fans of that character being understandably upset at the displacement, rather than desire to see the sidekick remain a sidekick. When that sort of thing happens, it's most often remedied by simply having the character graduate again, creating their own hero identity and handing the Legacy Character baton back to its proper holder.

Comic Books

 * Wally West, aka the Flash, previously the greatest example of this trope, is now the greatest subversion. After the second Flash, Barry Allen, died in the Crisis On Infinite Earths, Wally stepped up from the role of Kid Flash to Flash. Over the course of a quarter-century, he appeared in more issues of Flash than Barry, in far more spin-off comics and team-up books, was a founding member of four different incarnations of the Justice League, appeared in the Justice League animated series, and acquired his own stable of supporting cast. Then Barry came back, Flashpoint happened, and in The New 52, Wally has been Ret Gone'd, along with most of his supporting cast. His graduation stuck so hard, Geoff Johns had to wipe him from the universe in order to un-stick it. (Bonus points for Barry being personally responsible for the wiping.)
 * Bart Allen is another subversion. Originally Impulse, then Kid Flash, then the Flash, then dead, then back to Kid Flash, then The New 52, and now he's a different Kid Flash.
 * Batman's sidekick Dick Grayson became Nightwing, and has never returned to being Robin; unlike many characters with successors, he's never referred to as the "real" Robin, just the first.
 * Arguable exception: in the storyline following "Knightsend", he became Batman briefly, then returned to being Nightwing. This was, however, always intended to be temporary.
 * And then he became Batman an a more permanent basis with Bruce Wayne's 'inconveniencing' in the event Final Crisis. Fans guessed this would be reverted as soon as Bruce got back, but it actually stuck around for a little while with both men operating as Batman - in fact, Bruce is franchising and appointing even more Batmen worldwide. It'll eventually be reversed by the post-Flashpoint relaunch.
 * The Batman Inc franchising hasn't been abandoned. However, Dick Grayson was demoted to Nightwing (again) thanks to the New52. This, despite showing that having two Batmen worked. And considering Bruce Wayne alone stars in four or five books, having a second Batman might've helped.
 * The second Robin, Jason Todd, graduated once he came back from the dead. Except instead of becoming his own hero he became a villain. Or a really dark Anti-Hero or something; it's complicated. He's tried to hijack the Batman and Nightwing names a couple times, but for the most part he's taken over the pre-existing name the Red Hood.
 * Also, in an Alternate Universe where he didn't die, he becomes the second Batman.
 * Tim Drake, the third Robin, altered his identity into Red Robin. And yes, this counts as a full graduation, as Damian Wayne has taken over being original-style Robin.
 * The original Speedy has long since moved on from being Green Arrow's sidekick, becoming first Arsenal, then Red Arrow, then Arsenal again.
 * Donna Troy stopped being Wonder Girl, and started being... well, we won't get into that. Almost nothing's stuck without having new layers of convoluted continuity added on, but she's still not Wonder Girl again.
 * She's a really unique case. Both the confusion and Donna's subsequent promotion stem partially from the fact that Wonder Girl was originally supposed to be Wonder Woman as a young girl who occasionally interacted with her adult self via Time Travel. A writer saw the cover for one of these stories and got confused when he was writing the Teen Titans.
 * Borderline exception: Stephanie Brown, the Spoiler, "graduated" to replace Tim Drake as Robin. It lasted only a few issues, and she then returned to being the Spoiler... but only for the Bat Family Crossover that ended with her death. (She's Just Hiding, actually). Now she's graduated again to be the current Batgirl. As of the post-Flashpoint relaunch, Barbara took the mantle of Batgirl back. Stephanie Brown Butt Monkey of the Bat Family
 * Zig-Zaged: while Barbara Gordon shows no signs of abandoning her role as Oracle to become Batgirl again, there is substantial -- though far from universal -- desire to see that happen. This is likely due to the changeover being connected with her being paralyzed. However, there is just as substantial support for Babs to stay as Oracle, as she is a rare example of a handicapped hero whose concept doesn't rely on a Disability Superpower or on being Inspirationally Disadvantaged.
 * As for the other major Batgirl, Cassandra Cain, she stepped away and gave the role to Stephanie. She was eventually appointed as the "Batman" of Hong Kong, using the code name "Blackbat".
 * An unusual example: Moon Knight reluctantly took on Midnight--the son of one of his enemies--as a sidekick. Eventually Midnight was "promoted" to villain status, after becoming an evil cyborg. This graduation stuck until Moon Knight recently euthanized his old charge.
 * After Civil War Steve Rogers was killed, and was replaced as Captain America by Bucky Barnes, his WWII sidekick. You thought Bucky was a Dead Sidekick? It's a long story... Anyway, when Steve came back, they decided that Bucky should be the one to continue on as Cap, as it's helping his Character Development. Steve now operates sans codename as a super-agent not unlike Nick Fury.
 * Though recently Bucky went back to the Winter Soldier codename after supposedly dying during Fear Itself. He still operates as a hero, and will be getting his own independent on-going series next year.


 * Miracleman saw his sidekick, Kid Miracleman, grow up and become...a homicidal lunatic who horribly tortured and killed millions of people. Sometimes these things don't work out like you'd hoped.
 * Subverted and lampshaded in recent issues of The Incredible Hulk. With Bruce Banner safely locked away in a military base and unable to turn into the Hulk, a new, Red Hulk (called "Rulk" by fans) shows up from out of nowhere. Who is he? All signs pointed to Rick Jones, the original Hulk's old sidekick, having graduated into the role...which just made it all the more shocking when we learn that Rick has graduated, but NOT into the Red Hulk...instead, he's become a creature called A-Bomb, strong enough to fight Rulk on his own level.
 * Granted, Rick was Captain Marvel on at least two previous occasions.
 * Aqualad was the last of the original Teen Titans to get a new name. When it happened, though, he got an entire miniseries in which, as well as the name Tempest, he got new water-shaping powers.
 * The current Knight (the "Batman of Britain") is the original Squire. Admittedly, the Knight and Squire hadn't appeared anywhere for about fifty years until this version showed up, so it was less a change in the status quo and more the introduction of a might-as-well-be-new character...
 * Similarly, the Ranger of Austalia was killed during his reintroduction, and his sidekick Scout took over. Chief Man-of-Bats' sidekick Little Raven went the more Nightwingy route of creating his own adult identity (Raven Red). Man-of-Bats still tends to call him Little Raven, though.
 * Vayne Aurelius #2 of Mana Khemia Alchemists of Al Revis becomes "Alchemy Man" to combat his Mentor, #1/"The Flay", when he became an Evil Overlord, the "Flayvor of Evil".

Literature

 * Tony Foster, hero of the Smoke series by Tanya Huff, was previously the sidekick of vampire Henry Fitzroy in the Blood series. Now, the tables have turned, and Tony is the hero, while in an astonishing reversal, Henry becomes Tony's Older Sidekick.

Live-Action TV

 * In Doctor Who, the Doctor and his companions aren't exactly superheroes and sidekicks, but three of his companions have gone on to have major roles in holding down the fort in modern-day Earth: in The Sarah Jane Adventures, Sarah Jane Smith and the meddling kids solve weirdness they're alerted to by "Mr. Smith," Sarah Jane's ultra-supercomputer. Jack Harkness is the leader of The Men in Black in Torchwood. Martha Jones doesn't have her own Spin-Off (yet) but she Took a Level In Badass in The End of Time, saving the world freelance.
 * The only reason Rose Tyler isn't holding down the fort in modern-day Earth is because she's doing the same on a parallel version thereof. Mickey did it as well during series 2, though he eventually moved back to his own Earth. (In fact, there was originally supposed to be a Rose Tyler-based spinoff called Rose Tyler: Earth Defence, which got pretty far into pre-production before being cancelled by Russel T. Davies on the grounds that a spin-off would kill the emotional impact of her departure in Doomsday. Between what information we know and how she appeared in later episodes like Turn Left, it appeared to be something of a proto-Torchwood.
 * This seems to happen to everyone the Doctor takes on as a companion in the new series; they all grow from their time with him and become heroic alien-fighters in their own right. Davros brought this up during the season four finale, although he put a rather dark spin on it.

Web Original

 * In the Silver Age campaign, a now-adult former Kid Sidekick Tailgunner (who tagged along behind Golden Age hero Barnstormer) had come into his full powers and become the second Barnstormer.

Western Animation

 * Batman the Animated Series, just like in the comics, Dick Grayson leaves the mantle of Robin to become Nightwing.
 * Barbara Gordon going from Batgirl to Police Commissioner could count too.
 * Young Justice has one of these pretty early on with Green Arrow's sidekick Speedy Rage Quitting and later coming back as the new hero, Red Arrow.
 * As of season two, Robin is now Nightwing, with Tim Drake taking up the Robin identity.