Also, Lex takes advantage of the situation to pull off Flash's cowl and discover his secret identity but is thwarted when he has "no idea who this is." In one Silver Age story, Heat Wave managed to unmask (Barry Allen) Flash and had much the same reaction.
A political pundit cites a book titled The Innocent Seduced as a source proving the link between the Justice League and juvenile delinquency. This references Seduction of the Innocent, the book which made many of the same claims and sparked the creation of The Comics Code Authority. This pundit, by the way, is G. Gordon Godfrey, who, was a full-on agent of Darkseid in Jack Kirby's New Gods series (better known as "Glorious Godfrey").
Snapper Carr, sidekick/teen mascot of the Justice League in the comics, gets screen time as a reporter.
The episode "Legends". That's all that needs to be said (although even those savvy to the comics may not have caught the reference to Roy Thomas in the form of "Roy Thompson").
The same episode also features the Justice League fighting a giant robot that looks extremely similar to one of the title mecha from Neon Genesis Evangelion, a popular anime series Bruce Timm has drawn fan art of in the past.
Also, "The Savage Time". The writers took the opportunity to cram as much WWII comics nostalgia into the three-parter as humanly possible.
Similarly, in another time-travel episode, John Stewart briefly turned into Hal Jordan as the timeline fluctuated.
There's even a Marvel Mythology Gag in there, as Superman smashes a plane and is covered with burning fuel, briefly resembling the WWII hero the Human Torch (not to be confused with the later model by that name)
It starts even before the setting shifts to World War II. The alternate-timeline Batman refers to the group of freedom fighters he started in the absence of the Justice League as "orphans and outsiders." In the 1980s, Batman left the Justice League to found a new team called the Outsiders. Naturally the background characters include cameos by the B:TAS Robins and Batgirl, and a young Cassandra Cain.
"A Better World" started out on paper as an episode featuring the Crime Syndicate of America, an evilAlternate Universe version of the Justice League.
The Royal Flush Gang (first incarnation) are voiced by the actors who voice the main characters in Teen Titans.
Another Teen Titans reference in "Patriot Act," when Green Arrow calls for backup versus the Shaggy Man...and his ex-sideki— err, ex-partner, Speedy shows up (completing the Seven Soldiers homage). Same voice actor, look, and general attitude as his Teen Titans counterpart.
"Patriot Act" also has a Nazi scientist paraphrase the Golden Age descriptions of Superman's abilities when hyping up his Captain Nazi project. The fact this version of said project uses Super Serum rather than genetic alteration can be taken as another nod to Marvel.
Also in "Patriot Act". The heroes in the parade and the two backups are the present day versions of the Seven Soldiers of Victory, a World War II era team consisting of the Star-Spangled Kid, Stripesy, Green Arrow, Speedy, the Crimson Avenger, the Shining Knight, and Vigilante.
Speaking of "Flash and Substance", the episode also featured the Flash Museum, featuring more Flash Mythology Gag moments than thought humanly possible.
One more from "Flash and Substance" — Mark Hamill, who regularly plays The Joker in the DCAU shows, plays one of The Flash's foes, The Trickster. Essentially, he's reprising his role from The Flash live action TV show.
In "Secret Society", the scene of the League and the Society charging towards each other is a reference to the opening of Challenge of the Superfriends. Earlier, Shade jokingly refers to Grodd's Society as the "Legion of Doom".
In "To Another Shore," when Wonder Woman needs to switch from civilian clothes to her costume, she performs the spinning "transformation" sequence from the Lynda Carter TV series, complete with lightshow.
In "Eclipsed," Flash suggests to (John Stewart) Green Lantern that they go on a road trip "looking for America," which (Hal Jordan) Green Lantern once did with Green Arrow. He even describes them as "Hard-Traveling Heroes," the name of the story arc.
In "Maid of Honor," Princess Audrey refers to Wonder Woman as having "feet of clay," to which Wonder Woman responds "You have no idea." Wonder Woman was born when her mother sculpted a baby out of clay, and the gods brought her to life.
The last scene of the series shows the Justice League running down a flight of stairs in groups; each group has a common bond, such as being part of the infamous "Satellite era" or being Jack Kirby creations.
In the Legion of Super Heroes episode "Phantoms", Brainiac 5 refers to historical data on Superman's origin being lost in "the great crisis". This could be a reference to any number of things in the comics, but most likely, Crisis on Infinite Earths.
This is mentioned again by Brainiac 5 in "Message in a Bottle" as an excuse for not knowing who was "The Terror" that shrunk Kandor and put it in a bottle. This references how in The Silver Age of Comic Books it was Brainiac, but Post-Crisis it was a wizard named Tolos. (In this case, he's lying, badly, as it's very obviously Brainiac.)
"In the Beginning" showcases the original Legion founders and gives us a chance in flashback to see key team members in their "Disco Duds" (a.k.a. their classic Silver Age costumes plus epic The Seventies styling)
In "Phantoms," Drax's pets are modified giant versions of Bizarro Krypto.
In "Brain Drain," deranged, babbling Brainiac 5 either wants his hot cocoa or his comics-pet-space-monkey Koko.
He also starts listing off the umpteen colors of Silver Age Kryptonite.
"Mxyzpixilated" is extra-extraordinarily meta: Superman mispronounces Mr. Mxyzptlk's name exactly the way that the Super Friends production team decided to pronounce it. Mr. Mxyzptlk himself all but crosses the Fourth Wall, turning Jimmy into a turtle, making the Kents' cat flight-capable, and starring in his own private newspaper comic strip by "Siegel and Shuster," the creators of Superman.
"Little Big Head Man" shows Bizarro's created a model of a square planet, namely Htrae, Bizarro Earth from The Silver Age of Comic Books. Then Mr. Mxyzptlk's girlfriend Ms. Gsptlsnz summons up a real-life Action Comics issue advertising Mr. Mxyzptlk on the cover.
Teen Titans, while not as mythos-heavy as the DCAU (being separate from it), has its share of Mythology Gags as well.
In "Apprentice", Slade forces Robin to become his apprentice, and then states that he'd eventually become like a father to him. Robin's response? "I already have a father," while the camera pans up to a group of bats flying away.
Music that sounds awfully like the B:TAS opening plays as well, iirc.
One of Beast Boy's imagine spots has him jumping out of an old comic cover while a banner proclaims him the "new sensation of 1963." 1963 being the year Beast Boy first appeared.
Even better, Beast Boy was dressed up as Robin at the time. The composition of the shot (Beast-Boy-as-Robin bursting through a screen held by Starfire/Batman) is an homage to the cover of Detective Comics #38, Robin's debut. Only he was the new sensation of 1940.
The big fight scene for the episode takes place around a large neon sign, toppling an A and a Y, until the final wide angle shows what's left to read 'W_ _NE Enterprises'.
When a never-revealed mystery person takes up Robin's old Red X costume, Beast Boy speculates on who it could be—his board-o'-theories includes Jason Todd, an ex-Robin who'd similarly appropriated the identity Red Hood in the comics.
Another suspect is "Robin's Long-Lost Brother". Robin has an older brother who died along with his parents in Batman Forever. The brother shown on the board also visually resembles Scott Menville, Robin's voice actor.
In one episode they meet a magical kid from another dimension who is a huge fan of Robin. His name is Nosyarg Kcid. They decide to call him Larry instead.
Larry is an Expy of Bat-Mite, a similar Batman character now removed from comic book continuity...maybe.
In the episode where Mumbo captures the Titans and turns all but Beast Boy into animals, Starfire is turned into a cat. The original comic established that Starfire's people evolved from cats.
In "Lightspeed", one of these pops up as a Freeze-Frame Bonus - when Mammoth comes out of a store, the candy bar he's carrying is a Lightspeed Energy Bar, the same brand that Flash shilled for in an episode of Justice League. Fittingly enough, the bar is stolen out of Mammoth's hand by Kid Flash, who's being voiced by Justice League Flash's voice actor Michael Rosenbaum.
One DC Nation short has the Titans, thanks to Mad Mod's time machine (Built to resemble a British phone booth) has them transported to various time periods. When they reach the 80s, they're dressed like their comic counterparts.
The 90s part also features a few shout-outs to the "New Titans" era (1991-1996): Raven as a red-skinned demon, Cyborg with bulkier armor, Beast Boy with a mullet, and Starfire wearing the armor that Mirage used while impersonating her.
In the episode "Secret Origins" April O'Neil poses as a TV reporter to infiltrate a building, wearing a very familiar yellow jumpsuit; when she tries to "interview" the soldier supervising the blockade around the Utrom building (it's complicated), she explains that she's from "Channel 9 News *broken tag on jumpsuit flips down* er, Channel 6 News". Later, once the smoke clears, Donatello says April would make a good reporter, to which she replied "In another lifetime, maybe." These are all references to the previous Ninja Turtles cartoon, where April was a reporter for Channel 6 News.
The van is kept in a warehouse on "the corner of Eastman and Laird".
Turtles Forever, full stop! Not only do we have a crossover between the 2003 and 80s series, but a view of the multiverse shows pretty much every other continuity ever.
In the same episode, as the alien Utroms escape the under-siege T.C.R.I. building, one makes a complaint, to which the other says "Oh, shut up, Krang."
Note that both Krang ''and the Utroms were based on aliens that originally appeared in the original comic book series by Eastman and Laird.
A season four episode features anthropomorphic rhino Gennosuke, exploring NYC when he becomes taken with a muscular punk's outfit. One "shopping" trip later, he is seen wearing the outfit: a tight yellow wifebeater, cargo pants, and an ammo belt strapped across his gut—the outfit anthropomorphic rhino Rocksteady wore in the original TMNT series. To complete the look, Casey Jones slaps a helmet on him as he leads the rhino away.
Leatherhead's lair is taken from the turtles' second lair in the movie series.
The other short, "Jesus vs. Santa", is the one the boys are working on in "A Very Crappy Christmas".
In the episode "The Passion of the Jew", when Stan asks for a refund over the phone, he says that he'll get his money back like he did for BASEketball, a movie that Matt Stone and Trey Parker both starred in.
Also counts as Self-Deprecation, as almost immediately afterwards, he and Kenny both agree that is was an terrible movie.
In Scooby-Doo on Zombie Island, there's a scene where Fred is going through his clothes while dressing... and comes across a bright orange ascot. "Nah", he decides. Animated versions of Fred haven't touched the ascot since the late 1990s.
At least The Mystery Begins redoes the intro to Scooby Doo: Where Are You!, and Scooby Doo and the Monster of Mexico is completely filled with references to the old show, including much of the soundtrack being redoings of the background music from that show.
Velma: An ancient ghost coming back after a hundred years to get revenge? Yeah right, who'd believe that?
Scooby-Doo and the Cyber Chase has the whole last section as a hurricane of references to the series, such as the outdated clothing, the monsters being fake, and obviously the returning monsters from the original series.
Beyond that, there have been cameos by other Hanna-Barbera characters. Pebbles and Bamm-Bamm appear as beach-goers in one episode, while Suzie Chan makes several non-speaking cameos as a student at the Mystery Inc. gang's high school.
The villain Alice May looks almost exactly like Gwen Stacy from Spider-Man, right down to her clothing and color palette. She's even shown wearing a spider pattern dress during her capture.
Velma dresses up as Cleopatra in the 1969 episode Scooby Doo and a Mummy, Too as she, Shaggy and Scooby hide from the mummy. She dresses up as Cleopatra again in Scooby-Doo! in Where's My Mummy? as part of the Scooby-Doo Hoax she helps stage.
The series actually begins with footage from the original 80s show (presented in the episode as history tapes)
In the first episode, when the Autobots are first attacked, Bumblebee says Rattrap's Catch Phrase "We're all gonna die, aren't we?"
He later once called Optimus "Big Bot", like Cheetor did for Primal.
When Bumblebee notes how weird it is that Prowl's vehicle form is a motorcycle without a rider, he suddenly makes a hologram rider like the one from the live-action movie (AKA Mustache Man).
The new version of Soundwave has eyes that change between the yellow of the original toy to the red of the G1 cartoon, and was first seen in a box resembling his G1 alt mode, and at one point he develops a shoulder cannon, and the fragment of him left at the end is based on the MP3 player Soundwave.
There's a double gag in the second season's "Garbage In, Garbage Out" with "I am Wreck-Gar! I dare to be stupid!": it referenced not only Wreck-Gar's Animated voice actor, Weird Al (who sang "Dare To Be Stupid"), but also the appearance of the original Wreck-Gar in the 80s animated movie (where the same song was played). In the same episode, Wreck-Gar throws the motorcycle altmode of his G1 namesake at Bumblebee. And, yet again in the same episode, he mistakes one of Lugnut's weapons for "the universal greeting", reaching for it as he says "Bah weep graaagnah wheep ni ni bong", another reference to his introduction in the G1 movie. At this point, it might be fair to just call the entire character a giant mythology gag.
In the same episode, Ratchet gives a ride to a married couple named Spike and Carly, who greatly resemble the late G1/Headmasters characters of the same names. They originally appeared in the background of the first episode, along with their son Daniel who's made a few recurrences himself.
Sari has a robot dog named Sparkplug, evidently named after the G1 character (Spike's father). A construction worker who strongly resembles him appears in a few episodes.
For Halloween, Sari dresses up as G1 Optimus Prime. Well, okay, she dressed up as Animated Optimus, and ended up looking exactly like G1 Prime.
When Megatron is trying to create a new body, he says he needs a substance called 'Destronium'; this is probably a reference to the Japanese G1 continuity, in which the Decepticons were called Destrons (and paralleling Cybertronium, as the Autobots were called Cybertrons in Japanese).
When the Constructicons are brought to life, they appear in the vicinity of a crane that resembles the alt mode of Hook, a G1 Constructicon. This is a whole season after they pulled a fast one by earlier showing a group of automated construction vehicles/mining equipment in G1 Constructicon colors, which are never seen again.
Though Mixmaster and Scrapper do eventually get G1-style paint jobs after officially becoming Decepticons.
In the last episode of the first season, the Autobots' ship is partially buried in a volcano, similar to what happened to the Ark at the start of G1.
Swindle mentions in passing that he has had dealings with the Vok. The Vok were incredibly powerful aliens that were the secondary antagonists in Beast Wars. Later, in the Season Three episode 'Decepticon Air', he mentions having dealt with the Quintessons, from the original movie and later seasons of the G1 cartoon.
And then there's a human villain called Headmaster, with a suit of Powered Armour that works in a very similar manner to the Headmaster suits from the aborted fourth series of Transformers Generation 1.
Starscream's clones (except the female one) all have color schemes copied from the other G1 Seekers — characters who were essentially Palette Swaps of Starscream or became similar F-15 jets.
The Sycophant: Sunstorm The Coward: Skywarp The Liar: Ramjet The Egomaniac: Thundercracker The Female: Japanese Transformer Overlord (according to Word of God); also resembles Generation 2 Ramjet.
The female clone's name is officially Slipstream, I believe.
Susan Blu, voice of the original Arcee, is now voice director for Animated, and got to briefly reprise her role in a flashback.
The Decepticon team introduced in season three is named "Team Chaar", after the planet the Decepticons moved to after finally being expelled from Cybertron after The Movie in G1. (Aptly enough, the Autobot team that fights Team Chaar is headed by Rodimus Prime, who didn't exist until after the movie.) It's unknown if Animated has its own planet Chaar, however.
Speaking of that episode, Waspinator is seen pulling himself back together while commenting "Waspinator has planzzz...", both trademarks of the oft-exploded original Waspinator in Beast Wars. However, while the original did both these things in a cute or humorous manner, Animated made them seem a lot creepier.
In Human Error Part Two, Scrapper has a Dinobot pet, and named him Snarl. When Sari asks, Scrapper answers, "Well, I was going to name him Slag, but I think he took it as an insult." Probably a double callback, as the original character was named Slag, and this was both a curse in Cybertronian and, in the UK, a lesser-known word for "slut," meaning the toy was not sold there much and necessitating a name change.
And now as of "Decepticon Air," Ramjet (Liarscream) and Sunstorm (Sycoscream) have shiny new helmets courtesy of Swindle — helmets that just so happen to match the heads of their G1 predecessors.
In "Endgame, Part 1", the Omega Clones resemble the Dark Guardians, the giant robots that the Quintessons used in Generation 1 to keep the ancestors of the Cybertronians in line. Fitting, seeing as how G1 Omega Supreme was a surviving Dark Guardian reprogrammed and made sentient as an Autobot.
The mysterious alien Alpha Q is based the G1 Quintessons, although he only has three faces (G1 Quintessons had five). In fact, in the comic, his full name is Alpha Quintesson.
Transformers: Shattered Glass can get downright labyrinthine. For instance, in Shattered Expectations, Dirge shows up in a body based on Games of Deception Dirge, in Beast Wars II Thrust's colors, in a pose mimicking Ramjet in Transformers Generation 2, bursting from a Pretender Shell based on Descent into Evil Dirge, in Chromia's colors, in a pose mimicking Octopunch from Generation 2. And this is ONE CHARACTER ON A SPLASH PAGE.
Arcee admires Bumblebee's new paint scheme after they go into hiding: black with yellow highlights instead of yellow with black highlights. She comments that she couldn't do that, since she would be mostly pink, which was her G1 scheme.
Soundwave is The Silent Bob, able to carry on a complete conversation despite never speaking or even having a face. He can speak, but he only does so once, a straight call back to G1: "Soundwave: superior. Autobots: inferior."
The Simpsons episode "Lisa's Sax": "Tracey Ullman was entertaining America with songs, sketches, and crudely drawn filler material." That filler being the early Simpsons shorts.
In "Treehouse of Horror XIII", Homer makes clones of himself. One of them resembles his old design from "The Tracey Ullman Show".
With the same voice.
And catchphrase (the 'Frosty Chocolate Milkshakes' line)..
Another episode has the family recreating their family photos, including one that says "Happy 1987." Bart, Homer, and Lisa look like their Tracy Ullman counterparts before shaking their heads and reverting back to normal.
In another episode, the family is watching FOX's latest round of animated programming. Homer comments that animated shows are great "because they don't have to pay the actors squat!" Flanders then walks by, speaking with a different voice. At the time, the Simpsons' cast had been engaged in very bitter salary disputes with senior management.
As in many animated shows, the characters have frequently made reference to their unchanging wardrobes.
In one episode Homer says to Bart, "Where's your blue shirt?" and Bart responds, "I don't have a blue shirt" referencing the blue shirt Bart tends to wear in knockoff merchandise.
In "Itchy and Scratchy the Movie", Lisa tells Bart that the eponymous movie had cameos by Dustin Hoffman and Michael Jackson: "They didn't use their real names, but you could tell it was them!" Both appeared in classic episodes of The Simpsons under pseudonyms.
In "Das Bus" Bart tries to entertain his classmates by singing "Do the Bartman" (a novelty hit single his character had in the early 1990s). Ralph's reaction: "That is so 1991."
Another episode "Sweets and Sour Marge" has Chief Wiggum attempting to burn Butterfinger snacks, but as he puts it "Even the fire won't take them". Bart Simpson was the mascot for this brand and made TV commercials to endorse the product.
In Code Lyoko Season 4, the large room in Sector 5 that houses the Skidbladnir is called "Garage Skid" by Odd. This is a reference to Garage Kids, a short film by the creators of the show that was a test pilot for the series.
On SpongeBob SquarePants, Krabs refers to SpongeBob as, "Spongeboy, me Bob!" rather than "SpongeBob, me boy!" in the episode "Squeaky Boots". On a later episode, "Frankendoodle", the titular doodle is first named Doodleboy, then later is called DoodleBob. These are references to SpongeBob's original name, Spongeboy, which was changed for legal reasons.
The Batman features a bunch of references to classic Batman comics.
The future-based episode "Artifacts" has a scene where an aged Batman steps out of his Batmobile to fight Mr. Freeze. Freeze greets him with the words: "The Dark Knight Returns!".
Alfred also resembles his counterpart from the story, being a lot older and needing to use a cane to walk around.
There's also a tank-like Batmobile ala TDKR.
In the same episode, Robin and Batgirl assume their present-day comic identities of Nightwing and Oracle respectively.
Ellen Yin seemed to be based off on Ellen Yindel from The Dark Knight Returns and is hinted in "Artifacts" to have replaced Gordon as Commissioner like Yindel did in TDKR.
In the same episode during some speculation, Robin and Batgirl are referred to respectively as Red Robin and Batwoman.
Mr. Freeze suffered a similar, though less severe, deterioration as his Batman: The Animated Series incarnation and hence has replaced his legs with robotic spider legs.
In the episode "Team Penguin", the other members of Cobblepot's Legion of Doom keep suggesting different names for the group. Ragdoll comes up with "Villains United", the title of the book that introduced the Secret Six.
When the opening sequence changes to showcase Robin, he appears bursting through a circular a screen. As mentioned in the Teen Titans section, this is a reference to the cover and title page of Detective Comics #38, the 1940 issue he debuted in.
The pilot episode starts with Robin, Kid Flash and Aqualad as the main characters. The original Robin, Kid Flash, and Aqualad were the founding members of the Teen Titans, and their adventures together were chronicled in The Brave and the Bold.
"Schooled" contains an homage to the school bus rescue scene from the original Superman movie.
The same episode features Bruce Wayne accessing his Batsuit via a hidden switch in a Shakespeare bust, referencing the old Adam WestBatman show.
The Justice League's official logo (seen on membership cards and TV programs) is the title card from Justice League.
In "Misplaced", Captain Marvel utters the phrase "A world without grownups!" JLA: World Without Grown-Ups was the mini-series that first introduced Young Justice in the comics.
The opening scene of "Insecurity" has Black Spider in a parallel of the opening shot of The Spectacular Spider-Man, which was the previous series of show runner Greg Weisman. As a Casting Gag, the same actor who voiced Spider-Man in the show was brought back to voice Black Spider in his brief appearance.
The captive Roy Harper first seen in "Auld Acquaintance" is missing an arm. In the comics, Roy had one of his arms chopped off during the controversial Justice League: Cry for Justice mini-series.
"Bloodlines" has the Flash telling a young mother to seek shelter at "Fox and Gardner". Gardner Fox was the name of a prolific comic book writer who created (among many other things) the original Flash and Justice League.
The Leaguers that disappeared for sixteen hours during the events of "Auld Acquaintance" are as follows: Batman, Superman, Wonder Woman, Hawkgirl, Martian Manhunter, and Green Lantern (John Stewart). They were six of the original team members in Justice League, and also made up the Justice Lords in that series.
The Halloween Episode "Secrets" has Mal Duncan in Superboy's original costume from the comics, complete with sunglasses, which he calls "Superman, done right". Conner doesn't seem impressed.
Iron Man jokingly mentions needing an electrical socket or a pair of batteries to recharge his armor at several points. While this would seem ridiculously outdated today, he did indeed use those to recharge his suit back in the Silver Age.
Black Widow is stated to have "Champion-class" security clearance in the S.H.I.E.L.D. organization. In the comics, Black Widow was part of a team of superheroes known as the Champions.
Hawkeye sarcastically states that the team should move to the West Coast at one point. In the comics, there was indeed a team known as the West Coast Avengers, lead by none other than Hawkeye himself.
Hawkeye and Black Widow are introduced as SHIELD black-ops agents rather than reformed supervillains like in the original Avengers comics. This concept was introduced in The Ultimates, a modern day Alternate Universe story.
Hawkeye tries to piss off Chemistro in one episode by pretending to mistake him for Paste Pot Pete and the Hypno-Hustle, two outdated D-list Marvel villains.
The show uses J.A.R.V.I.S., Tony Stark's AI system from the original Iron Man movie.
When trying to rebuke claims that Hulk and Red Hulk are not one and the same, Maria Hill mentions that she heard the Hulk "used to be gray". While his green form is the most iconic and well known iteration, the Hulk was indeed colored gray in his earliest Silver Age appearances, and he's returned to that form several times since.
When Cassie Lang, the daughter of Scott "Ant-Man" Lang, is kidnapped, Hank Pym shoots her with Pym Particles, shrinking her down to a tiny size. After being rescued by her father and restored to her normal size, Cassie asks her father if they can "do that again." In the comics, Cassie would eventually become the size-changing Stature of the Young Avengers
One episode features one huge mythology gag. It's a bunch of kids telling their "Rashomon"-Style stories about the Batman, one being 60's campy, one being Miller's Dark Knight, and at the crowning moment of funny they stumble upon a very feminine boy stroking a feather boa saying, "I love Batman, that rubber costume, the car that can drive up walls," and another kid remarks something along the lines of, "oh please give me a break Joel," an obvious reference to Joel Schumacher and his Batman movies.
And another one was all-but an homage to the 1960s "campy" Batman starring Adam West... who, appropriately, voiced himself as "The Gray Ghost" and his actor.
Kim Possible alluded to how the show was going to end in the episode "Bad Boy", as Kim and Ron are watching their favorite prime-time soap, "Agony County", and complaining about the status of one couple. A few episodes later, "So the Drama" ended with Kim and Ron getting together, and was supposed to be the Grand Finale, until the producers decided to bring the show back.
Ron: Oh please, are they still teasing that Charity and Dannie are gonna get together?
Kim: Like that's ever gonna happen. It would end the series.
In the Batman Beyond episode "Out of the Past", Ra's Al Ghul attempts to use the Lazarus Pit to restore Bruce's youth before putting his mind in his body. He mentions that he will take over Bruce' empire by claiming to be the long-lost son of Bruce and Talia, which is a reference to Batman: Son of the Demon where Bruce and Talia conceive a child (who, since the end of the series, was reintroduced to the comics as Damian Wayne).
"Heroes" had three superheroes using the name "the Terrific Trio", which was originally used in the campy 60's series, which was the Dynamic Duo, plus Batgirl.
This rather obvious one occurs in "The Call" when Terry is fleeing from Superman using the flying Batmobile:
Terry: What's the top speed on this thing?
Bruce: Mach 3.
Batman: Is that faster than a speeding bullet?
In the series finale of As Told by Ginger, she shows all of her friends the book she's written about her life. The picture of her on the book is the original character design from the unaired pilot.
Danger Mouse: In "Penfold Transformed", Greenback dresses Stiletto in a Penfold costume to counter Dr. Crumhorn's Penfold robot (planted with DM to replace the kidnapped real Penfold). Stiletto makes a reference to Greenback's ill-fated Penfold duplicator (or magnetic molecular molder) from the earlier episode "Tiptoe Through the Penfolds."
In an episode of Count Duckula, the count is wearing a nightshirt with Danger Mouse's "DM" logo. Duckula first appeared on Danger Mouse as an antagonist.
In their early days, Hanna-Barbera would make outright stars of characters either referenced earlier or appearing earlier. Quick-Draw McGraw's name was first seen on a note on a door in a 1957 episode of The Ruff And Reddy Show (the studio's first series), Snagglepuss was an antagonist on the Quick Draw show, Ricochet Rabbit (from The Magilla Gorilla Show) first appeared as an antagonist on Touchè Turtle, and the Ant Hill Mob was first seen as a gang on insect bikers in an episode of Atom Ant.
The Problem Solverz references its [adult swim] pilot Neon Knome in some episodes. Kevin, the magic cup, can be seen in Horace's room, and the pictures on the wall are screenshots from the pilot. Roba also has a collection of Narrator dolls, and the giant Rollerblade appears in a few backgrounds. In "Hamburger Cavez", Roba unrolls his long sleeping bag the same way he did in Neon Knome.
In the Ultimate Spider-Man episode "Beetle Mania", the other heroes each have an Imagine Spot of how they could defeat the Beetle single-handedly. In each, he's wearing a different version of the green-and-purple armour from the 616-universe comics (except Nova, who for some reason imagines him as an actual beetle). When the Beetle actually appears, he's wearing his metallic Ultimate Universe armour.
In the pilot episode, a S.H.I.E.L.D. agent can be seen testing out webbed glider wings that look exactly like those worn by Spider-Woman.
In "Back in Black", Doop from X-Statix makes a cameo in Peter's fantasy sequence.
"Flight of the Iron Spider" contains a reference to the garage training sequence from the first Iron Man movie.
The watch Harry Osborn uses to contain his Symbiote is based on the one Peter used to contain his nanite costume in Spider-Man Unlimited.
In the pilot episode of Avengers Assemble, The Falcon's suit is referred to as "Project Redwing". Redwing is the name of Sam's pet falcon in the comics.
The trailers for the series heavily mimic Iron Man's infamous "Let's do a headcount" speech from the movie, complete with the "We have a Hulk" line.
The second episode has the team fighting the Space Phantoms. A Space Phantom was the lead villain of the second issue of the original Avengers comic book.
In the Halloween level of the Garfield game Garfield's Defense Force, Lanolin's costume resembles her Wicked Witch of the Wool outfit from the Garfield and Friends episode "The Ugly Duckling", minus the ruby slippers.
In the sequel to that game, Wade is wearing Roy's police hat from "Wanted: Wade".
"Hot Air" features a Who Is Driving? joke about Goofy, where he honestly answers he is while obviously not, just like in the famous short, "Mickey's Trailer."
The How-To Narrator who appears several times when Goofy is in focus, much like in Goofy's classic how-to shorts.
In "Close Encounters of the Weird Mime," Goofy's mime instructor holds up cue cards with pictures. When it comes to "duck", the picture is of Donald Duck.
In A Goofy Movie, in addition to Max having a Mickey Mouse phone and Mickey and Donald making brief cameos, when Goofy says he's taking a trip with his "best buddy", Max's first thought is that it's Donald.
In Godzilla: The Series, the H.E.A.T. team went to investigate a string of disappearances in Japan. Naturally, GodzillaJr. followed them there. After swimming across the Pacific Ocean, a Japanese girl in a passenger plane spotted him arriving at Japan.
Girl: Mommy look! It's Gojira!
Mother: Don't be ridiculous; what would Gojira be doing in Japan?