DC's All-Star Squadron featured the Young All-Stars, who were meant to replace the Golden Age versions of Superman (Iron Munro), Wonder Woman (The Fury), Batman (Flying Fox), Aquaman (Neptune Perkins, Tsunami), and Green Arrow (Tigress) Post-Crisis, because they, you know, weren't active back then anymore. Neptune Perkins was a very obscure pre-existing character, for what it's worth. They had Nazi-created evil counterparts called Axis Amerika to contend with, which were also retrofitted Expies of the vanished Earth-2 heroes: Ubermensch (Superman), Gudra the Valkyrie (Wonder Woman), Grösshorn Eule and Fledermaus (Batman ), Usil (Green Arrow) and Sea Wolf (Aquaman). Part of the reasoning was that, metaphysically speaking, iconic characters like Superman and Wonder Woman were "too big" to be replaced by just one new (and inevitably "lesser") character. The Token Japanese member of Axis Amerika, Kamikaze was an expy of Fawcett's Bulletman.
Archie Comics even had its own Expies of Archie, including That Wilkin Boy and Wilbur.
Fast Willie Jackson was an African-American Archie Expy from Fitzgerald Publishing.
Atlas/Seaboard comics published Vicki circa 1975... a feature that itself consisted of slightly-updated reprints of another Archie expy, Tippy Teen, which had been published by Tower Comics in the '60s.
Archie is also an Expy himself, being heavily-based off of Andy Hardy, a popular character played by Mickey Rooney at the time.
Todd Ziller (hmmm, what happens if we change that "T" to a "G") appeared in The Avengers. As a product of a kludge Super Soldier program, Project Troubleshooter, which shoved everything they could get into him (including Pym Particles, Mutant Growth Hormone, and etc.). Naturally this worked but in a real messy way and he became something that looked like the brother to a certain Toho monster. Mr. Ziller even has the code-name "American Kaiju".
Another expy to show in The Avengers, is the Shadow Colonel. He's a vampire in some very familiar black armour, German-style WWII helmet, a mask housing infra-red goggles with rebreather and a minigun. He's clearly influenced from Colonel Radec and Radec's own influence, the Kerberos Panzer Cop.
The Colleen Coover character Bandette was inspired by the French costumed heroine Fantômette, sporting an extremely similar costume.
Kirk "Man-Bat" Langstrom is to Curt "The Lizard" Connors. Really, regardless of where each character ended up, the only difference between their origins is the specific ailment they were trying to cure and the specific animal they were working on.
Carmine Falcone from Batman: Year One is made into one of Vito Corleone from The Godfather and introduces Falcone's family, who was similar expies for the Corleone children: his daughter, Sofia Gigante, is a Gender Flipped Sonny, while his sons, Alberto and Sonny are respectively ones for Fredo and Michael.
Calendar Man is used in a similar way to Hannibal Lecter, especially with Batman and Gordon going to him for help on the Holiday murders in The Long Halloween as Clarice Starling did with Hannibal on the case Buffalo Bill case in The Silence of the Lambs.
For one in the same property, Julia Lopez is one for Batman: The Animated SeriesCanon Immigrant Renee Montoya, including being an honest cop Gordon trusts, though it's implied she'd have a higher rank as the story implied she'll replace O'Hara as chief.
Tim Drake was initially written as one of Peter Parker. It's no secret that Chuck Dixon based Tim Drake's adventures on the first 50 issues of The Amazing Spiderman. Fans used to compare him to the iconic Marvel superhero, calling him the Peter Parker of Gotham.
The Batman Who Laughs from the Dark Nights: Metal crossover is inspired both visually and in motif by Judge Death a heinous monster who slaughters his entire universe simply because he can, and is inspired to bridge the gap to other worlds just to be able to do it all again.
Number 13, a strip about a supernatural family of monsters in the Anthology ComicThe Beano was The Munsters. Also Kat and Kanary is Sylvester and Tweety from Looney Tunes. The character Joe Jitsu from the 00s seems to be an expy of an earlier character entitled Karate Sid from the 80s.
Everett K. Ross from Christopher Priest's Black Panther was heavily based off of Chandler Bing. In fact, according to Priest, the character was even called "Chandler" in the early pre-production phase before they settled on an actual name.
According to Priest's website, Kasper Cole and his supporting cast were all designed to be intentional Expies of Spider-Man and his supporting cast, just with a deconstructive slant. Kasper is a relatable Everyman like Peter Parker, but is even more of a screw-up. His father, "Black Jack" is an Uncle Ben-like figure Kasper looks to for advice, except he's a corrupt cop in jail for drug possession. His mother Ruth is a double Expy, serving as both a stereotypical Jewish Mother version of Aunt May and the Marvel equivalent of Doris Roberts' character from Everybody Loves Raymond. Finally, Kasper's girlfriend Gwen is the requisite Gwen Stacy/Mary Jane-type character (right down to even being named after the former), except she's Korean and their relationship is completely dysfunctional, with Gwen constantly nagging and annoying him instead of being a source of emotional support.
In the Catwoman story "Selina's Big Score", Stark is a blatant Expy of Parker, Villain Protagonist of a series of crime novels by Richard Stark. He also looks like Lee Marvin, who played Parker (renamed Walker) in the film adaptation of the first novel, Point Blank. (Darwyn Cooke, who wrote and drew the story, later went on to officially adapt the Parker novels to the comic medium.)
Red Lion from Deathstroke is an Expy of Black Panther. Both are the respective rulers of an African nation, use an identity patterned after a big cat, and wear (very similar-looking) costumes made from nearly-invulnerable metals, complete with Absurdly Sharp Claws built into the gloves. The key difference is that while Black Panther is a just ruler and a hero, Red Lion is a cruel dictator and a mass murderer. Given that Red Lion was created by Christopher Priest, Black Panther's most famous writer, the similarities are definitely not a coincidence.
Diabolik had a major series of expies. Interestingly, these expies lost their readers and ended publication by staying true to Diabolik's initial noir while Diabolik and the only surviving expy (Paperinik) moved to other genres (Diabolik to crime fiction and Paperinik to superhero).
Marvel Comics' Donyell Taylor, originally codenamed Bandit, is an Expy of Marvel's own Gambit, a fact exploited shamelessly by an issue of Gambit's eponymous series when Bandit turns out to be romantically involved with Gambit's ex-wife Belladonna.
Lee, the main character of Peter David's Fallen Angel is an Expy of Linda Danvers, protagonist of David's previous run on Supergirl. In fact, David did his best to fuel speculation that the characters were one and the same until the book's second volume, in which he chronicled Lee's origins. Later on, he introduced Lin, yet another expy of Linda Danvers, who can in fact be considered Linda in everything but name. Likewise, the God figure in the series is a small girl dressed in a tennis motif and carrying a tennis racket, which makes her an expy of Wally, the god figure in David's Supergirl who was a young boy who carried a baseball bat.
John Byrne's college newspaper strip Gay Guy! had a villain called Charisma, whom no man could resist except... well, guess. Byrne liked the character concept so much that Karisma showed up on the Fantastic Four's doorstep a decade and a half later.
Final Crisis: Superman Beyond 3D features Captain Adam, an alternate universe version of Captain Atom who's a clear Expy of Dr Manhattan, sporting his blue skin, detached nature, and even a similar emblem on his forehead. This is fitting since Manhattan was originally an Expy of Captain Atom to begin with.
Ghost Rider villain Skinbender is plainly designed to heavily resemble Sailor Venus; true to this inspiration, she falls in love with Ghost Rider when they meet.
After season one of Arrow ended, Oliver was revealed to have a younger half-sister in the New 52, named Emiko, who is based on Thea Queen, his sister in Arrow, though Thea herself is an Expy of Mia Dearden. Both are experienced archers and have similar abilities, though Emiko is a teenager and Thea is an adult in addition to different racial backgrounds (Emiko is Eurasian [half-Caucasian/half-Japanese] and Thea is Caucasian) and different relation (Emiko is Oliver's paternal half-sister in the comics with her father being Oliver's father Robert Queen and mother being Shado, while Thea is Oliver's maternal half-sister in the show with her father being Malcolm Merlyn and her mother being Oliver's mother Moira Queen). This becomes Expy Coexistence when Emiko appeared in the seventh season of Arrow.
Hellboy fought against a vampire lord named Vladimir Giurescu that was obviously modeled after Dracula, sharing traits such as having many vampire brides and a similar appearance to his real life inspiration. What is more is that before his plans were ruined by Witchfinder Edward Grey, Giurescu sought to install his own secret domain in Great Britain during the 1880s (more or less the same goal as Dracula and in the same time frame where the novel took place).
In Howard the Duck vol 3, there is Suzi Pazuzu, wielder of the Doucheblade (Sara Pezzini, Witchblade), villains Ian Whippingham (Ian Nottingham) and Kenneth Flogg (Kenneth Irons), Cain and Abel of the Boarding House of Mystery, and the guests Splatter Gomorrah (Spider Jerusalem), Anthrax (Wesley Dodds, Sandman Mystery Theatre), Hellboozer (John Constantine, Hellblazer), The Interminable (The Endless, The Sandman), and Utah and Ravel (Nevada and Bolero, Nevada).
Steve Gerber's creator-owned character "Leonard the Duck" was an expy of Howard the Duck, also created by Gerber, but owned by Marvel Comics. In fact, Leonard's introduction was a complicated situation where Gerber tied a Spider-Man and Howard crossover he was writing for Marvel with a Savage Dragon and Destroyer Duck crossover he was writing for Image Comics, suggesting that Leonard actually is Howard under an assumed name, and the Howard the Duck who's appeared in Marvel Comics since then is a clone. The issue also mentions a Spider-Man expy, Spider-Crab.
An oft-mocked facet of early Image Comics was that every team seemed to have a Wolverine expy, who had blades on his hands, a bad attitude, and a mysterious past. And while it wasn't every team Gen¹³ and Stormwatch being the most notable exceptions this was true for most of them: Youngblood had Troll and Cougar (though the latter was arguably more influenced by Beast), while spin-off series Bloodpool had Wylder; Cyberforce had Ripclaw; Wild CA Ts had Warblade; Bloodstrike had Deadlock; and Codename: Strykeforce had Killrazor. Deadlock was probably the most obvious, since his first costume featured a mask nearly identical to Wolverine's.
Ragged Robin is similar to Crazy Jane from Grant Morrison's Crazy Jane from his run on Doom Patrol. According to Morrison himself, they're the same person in a different universe. More of this on The Other Wiki. Alhough Ragged Robin does diverge from Crazy Jane and he invented a completely new Backstory for her.
King Mob's imaginary (probably) alter ego Gideon Stargrave is a blatant Expy of Michael Moorcock's protagonist Jerry Cornelius. Right down to the narrative caption boxes mimicking the typical chapter titles and prose styles of the Cornelius stories. It later turns out that the Cornelius stories exist in-universe and King Mob was consciously imitating them.
Lewis Brodie, the Outer Church agent who captures Fanny and King Mob in "She-Man", is a parody of Bodie from The Professionals, who was played by Lewis Collins.
All of the "Division X" characters are Expies of figures from 1970s British police series:
There was one issue of Justice League of America written in 2000 by Greg Weisman, in which the League travels to Paris and meets a clan of gargoyles living in Notre Dame cathedral, all of whom are clear Expies of the main cast of Weisman's cult classic TV show Gargoyles. There's the leader, "Behemoth" (Goliath), his ex-lover "Diabolique" (Demona), his daughter "Angelique" (Angela), his second-in-command "Montmarte" (Brooklyn), Angelique's lover "Montparnasse" (Broadway), the diminutive smart guy "Champs-Élysées" (Lexington), the team mentor "Seine" (Hudson), the Team Pet "Left Bank" (Bronx), and Behemoth's Evil Twin "Thomeheb" (Thailog).
When the teen supervillain Kid Karnevil attempted to infiltrate the Justice Society of America, he did so by posing as a patriotic superhero named the All-American Kid. All-American Kid's costume and backstory were extremely similar to those of Bucky, the sidekick of Captain America.
One story in The Maze Agency featured a detective named Senor Lobo, whom writer Mike Barr has acknowledged was a deliberate homage to Hercule Poirot.
Legends of the Dead Earth: In Legionnaires Annual #3, the imprisoned superheroes whom XS meets on Almeer-5 in the 100th Century are all inspired by major Marvel Comics characters. The first two are Gender Flipped expies: Ava / Avatar, who receives her powers from the Spear of Destiny, is based on Thor while Melissa Trask / Metallica, a brilliant electronics engineer who built an armored suit for herself, is based on Iron Man. Bob Brunner, who was transmorphed into Behemoth due to an energy transfer accident, is based on the Incredible Hulk. He resembles a blue version of the Hulk but, unlike the Marvel Hero, retains his intelligence when he changes. Ultra-Man, a very powerful hero from an earlier time, is based on Captain America.
The title character of Tekno Comix's Mickey Spillaine's Mike Danger is very explicitly Mike Hammer under a different name — according to the book's writer, Max Allan Collins, the name Spillaine originally intended him to have — and then Human Popsicled into the future. This is straight-up stated in the text piece at the back of the first issue.
Violet Paige, the protagonist of Mother Panic, is a Gotham City socialite, a half-orphan, and uses highly brutal techniques while operating as a vigilante. She is a skilled martial artist, works independently of Batman, has green eyes, and opts for a punk-esque aesthetic in her civilian identity. All these characteristics are shared by the second Batwoman, Kate Kane.
Detective Gould from Matt Kindt's Red Handed is an expy of Dick Tracy. He wears a very similar suit and hat, has an array of retro-futuristic gizmos, and is named after Tracy creator Chester Gould.
Marvel/Star Comics' Royal Roy was basically an Expy of Harvey Comics' Richie Rich, back when the latter company wasn't publishing any books in the early 1980s. It was even handled by the same artist/writer team that created Richie Rich.
When Jack Kirby and Joe Simon took over DC's Sandman book, they immediately made him more like their old assignment (Captain America) by turning him into a more traditional superhero, right down to giving him an Expy of Bucky in "Sandy the Golden Boy."
Dan Slott's run on Silver Surfer blatantly turns the Surfer into an Expy of the Doctor if he unambiguously lived in the Marvel Universe, being a superbeing who wanders around fighting evil, and shows a young Earthwoman with whom he has Unresolved Sexual Tension the wonders of the universe.
Archie's Sonic series has Doctor Finitevus, an obvious Expy of Doctor Zachary from Sonic the Comic. Let's see. Is an Evil Albino? Check. Has the "doctor" title attached to his name? Check. Is an echidna and one of Knuckles' people? Check. Has a fixation with Chaos Energy? Check. Has manipulated Knuckles (either by exploiting his character, or via brainwashing)? Check. Has had a powerful minion who was powered up by Chaos Energy? Check.
Not too long ago, during Marvel's Dark Reign event, the Sinister Spider-Man title (Mac Gargan's Venom posing as Spider-Man) introduced us to Doctor Everything, a pretty blatant expy of Watchmen's Dr. Manhattan, right down to his... disturbing penchantfor nudity.
Spider-Man villain Sergei Kravinoff a.k.a. Kraven the Hunter is an expy of General Zaroff of The Most Dangerous Game. While Hunting the Most Dangerous Game has become a widespread trope, it's no coincidence that the comic book villain shares the Russian aristocrat background of the original.
In a probably deliberate example, since the character is a Redeeming Replacement for one of Spider-Man's worst enemies, Phil Urich the heroic Green Goblin is an expy of Peter Parker. Urich is an Unlucky Everydude who works for the Daily Bugle and has an Uncle Ben just like Peter (although Urich's doesn't get killed). In the Spider-Girl series, the two characters are close friends.
This trope is lampshaded in full during Spider-Verse by Pavitr Prabhakar, the Spider-man of Earth-50101. During the events of the story, he comes to wonder whether he and the other Spider-Men are mere offshoots of Peter Parker after noticing all of the similarities between his own and Peter's backstories as well as the overwhelming number of alternate Peter Parkers as Spider-Totems, triggering a minor Heroic BSoD. Luckily, a quick peptalk from Billy Braddock, the Spider-Man of Earth-833, snaps him out of this, saying that Pavitr is just as much of a hero as Peter, and that the latter could be an expy of him.
Dr. Aphra, of the Star Wars comics, has BT-1 and 0-0-0, assassin droids that look like an R2-D2/astromech and C-3PO/protocol droid respectively. Other than being jet black and brimming with weapons, of course.
Pre-Crisis Supergirl had a crush on Dick Malverne, a guy who liked Linda, suspected she was Supergirl, and was determined to prove it... right like Lois Lane and Lana Lang liked Superman/Superboy, suspected he was Clark Kent and were determined to prove it. Linda specifically tells Dick is her Lana Lang. A Young Love short story revealed that Dick always knew, but after a while he decided to keep Linda's secret to himself.
Supergirl's best friend Thara Ak-Var is inspired by Jean Grey, being another female hero bonded with a firebird-shaped cosmic entity.
Supreme from Image Comics is an Expy of Superman, obviously. Originally this was mainly in terms of power set and appearance in personality and outlook on the world, though, Supreme and Superman couldn't have been more different. When Alan Moore took over the series, his in-universe Continuity Reboot made the comparison much more explicit.
From the pre-Moore era, Kid Supreme was a fairly direct take-off of Kon-El from DC Comics, with almost the exact same appearance and personality. His short-lived solo series, however, owed a lot more to the contemporaneous Robin and Impulse series in its tone and status quo.
Happened all the way back during the creation of the X-Men by Stan "The Man" Lee himself. When creating the original team of five, Lee decided he wanted to re-use the character of the Human Torch, but with ice powers instead of fire. The youngest member of the team, and also the most irresponsible and hot-headed, with the opposite super power...
Abigail Brand's half-brother Lothi in the S.W.O.R.D spin-off has major similarities of appearance and personality to Tank Girl's boyfriend Booga. Each character is a Lovable Rogue who isn't as cool as he tries to be and looks like a humanised kangaroo (which Booga actually is). About the only difference is that he's green.
Riptide's father Storybook Smith is based off the Golden Age hero Johnny Thunder, with whom he shares Reality Warper abilities and a fondness for tacky, green, checkered suits.
The 2099 incarnation of the X-Men has a lot of members who are clearly evocative of some member of the original team. The most obvious are Xi'an (the paternal mentor figure ala Professor X), Skullfire (the leader with energy blasting powers and Power Incontinence, like Cyclops) and Bloodhawk (the mysterious, brooding loner with anger issues and claws, as in Wolverine).
DC's Bumblebee is an obvious Expy of Marvel's Wasp. Everything from the power set, to her costume to the double-banger name (Janet Van-Dyne vs. Karen Beecher-Duncan). Karen did not start out this way but later writers added in the size shifting and after her marriage to Mal Duncan she hyphenated her name to seal the deal.
Miss Martian is this to pre-Crisis Supergirl. Executive Meddling prevented the writers from adding Kara into Teen Titans, so the writers instead created a completely different bubbly teenage alien girl that they could use. Miss Martian is often considered an expy of Starfire as interpreted in the Teen Titans cartoon, however that's probably unintentional.