The Movie featured an assortment of original songs that were obvious tributes to numbers from classic American musicals. Oklahoma! got quoted quite a bit ("Mountain Town"/"O What a Beautiful Morning"; "Uncle Fucka"/the title song; and "It's Easy, Mmmkay?"/"The Farmer and the Cowman"), but there were others. "Kyle's Mom's a Big Fat Bitch" was a pretty generic tribute to early 1900s musicals in general, complete with a "showstopper" climax followed by a "Good evening, friends!" finale. "La Resistance" is derived from "One Day More" from Les Misérables.
In terms of characters, the Secret Society of Cynics from "Ass Burgers" is heavily based on Morpheus's gang from The Matrix.
...and that guy was, in turn a pretty obvious Captain Ersatz of this guy.
Woody Woodpecker is a rather obvious copy of the early Daffy Duck and Bugs Bunny prototypes. No surprise, since the Bugs Bunny prototypes and Woody Woodpecker were made by Ben Hardaway, who was a prominent writer in the Woody Woodpecker cartoons after he left Warner Bros. for Universal Cartoons.
Mel Blanc himself voiced Woody for his first few appearances (and invented that famously annoying laugh) before being replaced because of his contract with Warner Bros.
Tantrum from the episode of that show with the same name is a Captain Ersatz of the Incredible Hulk.
Even Black Lightning villains get Ersatzed. The Justice League Unlimited episode "Double Date" features the crime lord "Steven Mandragora", a Captain Ersatz for Kingpin-esque albino villain Tobias Whale, who was the primary adversary in the original Black Lightning comic series.
JLU featured a thinly-disguised Captain Ersatz for Aquaman villain Black Manta, "Devil Ray." (Aquaman and related characters were off-limits while a live-action CW series was in development.) This was lampshaded in an actual issue of Aquaman, where someone mistakenly thinks Black Manta is actually called Devil Ray.
Justice League also had Aresia and Tsukuri, who were heavily inspired by the heroines Fury and Katana, right down to wearing very similar costumes. According to Dwayne McDuffie, Tsukuri was partially based off Lady Shiva as well.
While featuring characters who mostly predated the Marvel versions by decades, the team-ups between Dr. Fate, Aquaman, and Solomon Grundy, were meant to mirror Marvel's Defenders (Fate = Dr. Strange, Aquaman = Sub-Mariner, Grundy = Hulk. The latter even acted and talked like the Hulk on the cartoon). They were later joined by AMAZO, a Silver Surfer mirror. Hawkgirl was the stand-in for Nighthawk.
Batman: The Animated Series episode #18, "Return of the Gray Ghost", has Simon Trent, the star of a 1950s "costumed crimefighter" TV show, finding out that he was the inspiration for The Batman — because as a child, Bruce Wayne used to watch the show with his father. The Gray Ghost is an Expy of both Will Eisner's The Spirit and Walter B. Gibson's The Shadow. But there's still a Captain Ersatz here, since Simon Trent/The Gray Ghost is provided by Adam West, the original TV Batman....
Superman: The Animated Series introduced Luminus and Mala, who were essentially Doctor Light and Ursa with the serial numbers filed off. There was also Angela Chen, who was essentially an Asian-American version of Cat Grant. She was even given Cat's job as a gossip columnist and her infamous rivalry with Lois Lane.
Mala's lover was Jax-Ur. While Jax-Ur is a supervillain from the comics, this Jax-Ur has little to do with his comics counterpart, and is General Zod in all but name.
Mala also existed in the comics but was a man.
One episode of JLU featured Supergirl and several other heroes going to Tokyo to fight a giant turtle with tusks, which flew by retracting its legs into its shell and replacing them with rockets, causing it to spin like a flying saucer, but which was definitely notGamera.
Also from JLU, the aforementioned "Defenders" fought... "Ic'thulutu."
In the Justice League episode "Legends," four of the leaguers get zapped into an alternate universe populated by parodic Captain Ersatzes of Golden Age DC heroes. (For example, there's the Green Guardsman, whose power ring doesn't work against aluminum.) In-universe, the John Stewart Green Lantern read all their comics growing up. The episode had originally been written to explicitly feature Justice Society of America characters, but DC Comics publisher Paul Levitz refused permission. This wound up being a fairly positive bit of Executive Meddling all around, both for the episode itself and because it allowed for greater use of JSA characters down the road.
The same episode featured the Justice League fighting a giant robot that looked almost exactly like one of the title mecha from Neon Genesis Evangelion. The commentary from Bruce Timm confirmed this was intentional.
Since Superman comics were undergoing a revamp at the time, the producers of the Ruby-Spears Superman cartoon weren't sure how to utilize Brainiac. Instead, they created an original character named Cybron.
Batman: The Brave and the Bold had an episode focusing on circus heiress/vigilante Katrina Moldoff, who used Kathy Kane's costume but was never once called Batwoman (Riddler derisively nicknames her "Bat-Lady"). Word of God says that DC requested the rename because they didn't want this character's negative traits causing a backlash against the just-debuted Kate Kane Batwoman character.
The same series featured Scream Queen, Equinox and Kru'll the Eternal, who were Captain Ersatzes of Silver Banshee, Libra and Vandal Savage respectively.
Teen Titans had Val-Yor, who was physically based off Captain Atom. Additionally, Private H.I.V.E. was based off the Guardian, Billy Numerous was Multiple Man, Larry was Bat-Mite, Tramm was Lagoon Boy, Sarasim was Sarah Simms, and Puppet King was the Puppeteer.
The legal fight between Disney, Amblin Entertainment and original creator Gary Wolf over ownership of Who Framed Roger Rabbit led to the creation of the TV series Bonkers. Especially noticeable since Bonkers himself, a Disney property, is more obviously based on a Tex Avery style character. Amblin Entertainment would come up with its own ersatzes in the form of Mindy and Buttons on Animaniacs.
Little Audrey was created by Paramount's Famous Studios to be a Captain Ersatz of Little Lulu, as Paramount didn't want to pay Lulu's creator anymore money for rights to the character. Both characters would survive for decades in comic books and eventually both wound up under the ownership of the same company.
Also Googily Goop, an obvious parody of Betty Boop.
From the black-and-white Looney Tunes, Buddy is both a Captain Ersatz and a Suspiciously Similar Substitute for Bosko. When Bosko's creators left WB for MGM and took the rights to Bosko with them, producer Leon Schlesinger quickly assembled a new animation team who hastily came up with the character of Buddy, who was, in Leonard Maltin's words, "Bosko in whiteface." The Buddy shorts are remembered for being particularly dull even by the standards of 1930s animation.
His follow-up, Beans the Cat, who had his spotlight stolen by Porky Pig, was an ersatz of Felix the Cat.
6teen uses this constantly, in fact the only thing they use that is the name of the real life thing is Star Wars:
Ironically, in the episode Nikki was annoying Darth's girlfriend (for those who remembers the plot) she and Jonesy saw a sci-fi movie that's an expy of Star Wars, but not the real one! Yet they had constant references in other episodes, namely around Darth!
Kappa Mikey, a parody of anime, contains tons of characters who are legal rip-offs of real anime characters, in the same vein as Drawn Together. The character Gonard gets bonus points, since he is believed by fans to be an expy of Goku, thanks in no small part to both of them sharing the same English voice actor!
Depending on whom you ask, The Dread Baron and Mumbly are either these, or Expys. According to some accounts, Hanna-Barbera was in a legal conflict with Heatter-Quigley (who was to have created a live game show segment for Wacky Races) over who owned the rights to the Dick Dastardly and Muttley characters, which led to the creation of the new characters for the show Laff-A-Lympics. Others point out that Mumbly actually pre-dated Muttley (though he originally was a good guy.)
Muttley, created in 1968, predates Mumbly, created in 1976.
Issue #13 of the Laff-a-Lympics comic book shows that Dread Baron and Dick Dastardly were brothers.
Heatter-Quigley was given an on-screen credit on Wacky Races despite the fact that the live game show segment they were to have made as part of the show was scrapped. The Heatter-Quigley billing appears nowhere on either ofthe show's spinoffs, but it does appear in the copyright tag of a Dastardly & Muttley comic book story, "Truce or Consequences" (Gold Key, Hanna-Barbera Fun-In #10, January 1972).
The Venture Bros. has quite a few. Dr. Orpheus is Doctor Strange. Jefferson Twilight is Blade. The Groovy Gang are a bunch of psychotic parodies of Mystery, Inc. from Scooby-Doo. Professor Impossible and his family are deconstructions of the Fantastic Four. There are a lot, and they're mostly played for laughs. Surprisingly averted with Jonny Quest, Race Bannon, and Dr. Zin. When the creators found out the same people own the right to their show and Jonny Quest, they had them make actual appearances. Later on, they had to start calling him "Action Johnny" for trademark reasons. Intellectual property law is a cruel mistress.
Almost every episode of The Simpsons has one. A few examples: Sherry Bobbins (explicitly), "Angelica Button and the Dragon King's Trundle Bed", Count Fudgeula, Itchy and Scratchy, Menthol Moose, Rainier Wolfcastle (married to Maria Shriver Kennedy Quimby)... the list goes on and on.
A Great Gazoo Ersatz called Osmodiar appeared in two episodes, "The Simpsons Spin-Off Showcase" and "HOMЯ".
Specifically, they fight elves who resemble the members of X-Men's Alpha Flight (A Canadian task force that served as part of Wolverine's backstory in the late 70's/ early 80's.) They are even given the Punny Name Elf-a Flight and the one with candy cane claws is called Wintergreen.
The Batman Beyond episode "Heroes" had three obvious references to the Fantastic Four in form of another superhero team called the Terrific Trio: the stand-in for Mr. Fantastic was changed to "the 2D man", the Invisible Woman gained ice powers and was dubbed Freon, and the Thing and the Human Torch were merged into one character, Magma. The idea is then ruthlessly deconstructed with the "accident" having been set up by a jealous admirer. Plus the mutation not only causes an end to normal life, but eventually psychosis. Then they all go rogue and die. And the captain of the SHIELD-like organization is not Nick Fury mixed with J. Jonah Jameson with a Hitler mustache.
The Tiny Toon Adventures spring break special very briefly shows a parody of Ren and Stimpy (in this case they're a squirrel and a chicken instead of a cat and dog) and Beavis and Butthead (who are portrayed as two furry animals, Beaver and Hoghead) here.
During the Daemon arc, Frisket, Matrix, Enzo and AndrAla encounter a mod user character who is a spoof of Austin Powers. While playing, Frisket reboots into a version of Mr. Bigglesworth, Matrix reboots into an exact version of Doctor Evil (complete with placing his pinky near his mouth in a sinister fashion if the shout out wasn't already enough), Enzo reboots into a version of Mini-me, and AndrAla reboots into a Fembot. In one scene, AndrAla actually shoots the Austin Powers user while trying to lure her in bed, as seen here.
In "My Two Bobs", there was also a Dragon Ball Z/Pokémon parody.
Almost all of the games are a Shoutout to various other pieces of popular culture, so if a episode featured a game (which it usually did) you're bound to find a few Captains or so among the cast.
Then there's the episode where people are mysteriously disappearing in Mainframe and two binomes show up to investigate: Fax Modem and Data Nully.
There is also an Ersatz of the Harry Potter universe. Harry Potter (a parseltongued wizard who can talk to snakes) is replaced by Nigel Planter (a partial-tongue "wizard" who can talk to snacks), Lord Voldemort is replaced by Lord Moldybutt (complete with the He-Who-Must-Not-Be-Named title), and Dean Toadblatts replacing Dumbledore in title and Snape in his attitude toward Nigel. It also featured Ersatzes of Draco and Hermione.
An episode of The Mask dealt with Stanley Ipkiss/The Mask spending time with and causing mischief with his favorite cartoon characters The Goofalototots Stinko, Pinko, and Snot, who are obvious expys of Yakko, Wakko, and Dot from Animaniacs.
Whenever a character from another series appears on MAD (often), their design is modified slightly to ward off potential lawsuits - even for characters that are owned by its parent channel Cartoon Network. Example: when Applejack appears in the "Cowboys andAlien Force" skit, she wears a floppy Southern Belle-style sunhat instead of her normal cowboy hat, has two bands on her tail and ponytail instead of one, has a variation on Rarity's cutie mark, and is colored reddish-pink instead of orange.
The Goode Family episode "Gerold's Way or the Highway" has a cop character who's a straight Captain Ersatz to the Angry Cop from the Harvey Birdman episode "Booty Noir", who is no better either.
The Marvelous Misadventures of Flapjack: In an attempt to ride the show's success, Disney tried to launch their own show called poopdeck with almost the exact same premise. When Cartoon Network found out, they had Disney cancel the show immediately on copyright basis and then made an episode devoted to the toying with idea with no small amount of vitriol ("Panfake", for those familiar with the episodes).
Star Wars: Clone Wars has the Jedi Sha'a Gi. Genndy says on the commentary he wanted to initially give him a more Shaggy-like voice, but thought it might come off as too goofy.
Star Wars: The Clone Wars: Savage Opress was explicitly created as the replacement for Darth Maul: the same species, the double-bladed red lightsaber, ferocious fighting style, and being Maul's brother no less. Ironically, he proved so popular with the crew and George Lucas, that the next move was to bring back Darth Maul himself and teaming the two up. Time will tell whether Opress ends up being Overshadowed by Awesome.
"The Box" episode featured no fewer than 13 bounty hunters, of whom only five made it to the end. To avoid killing off popular characters and to save production costs of making new models, quite a lot of them are palette swaps of pre-existing bounty hunters: Jakolli is an Expy of Greedo, Twazzi is an Expy of Rumi Paramita (from "The Bounty Hunters"), Mantu is an Expy of Chata Hyoki (from "Pursuit of Peace"), Sixtat is almost identical to a minor nameless character is "Wookiee Hunt".
On Scooby-Doo! Mystery Incorporated, Scooby and the gang could be considered Captain Ersatzes of the original Mystery Inc. (Ricky Owens, Cassidy Williams, Brad Chiles, Judy Reeves and Professor Pericles), only that previous team had since been corrupted by the thought of finding a cursed treasure. Ricky Owens' (Mr. E) van, the Enigma Machine, is definitely an ersatz version of the gang's Mystery Machine.
Going back even further, the original team were Captain Ersatzes of what was called the Benevolent Order of Mystery Solvers which dated back to the 1600s, when Crystal Cove was founded and a missing treasure corrupted each team's animal member which caused the dissolution of each team.