Brad who's practically a Disney equivalent of Dash.
The title character fell into this a lot, especially early on. Jake was quick to praise himself - only to fall flat on his face when things got tough. When he shed the ego, he'd be a force to be reckoned with.
Animaniacs: In the episode "Broadcast Nuisance", the Warner siblings provide (admittedly poor) service to Dan Anchorman, host of a news show, who has been shown to be arrogant, rude, demanding, and egotistical. Being rude to the Warner siblings is very bad for your mental health. (The Warner siblings have been shown capable of being polite and apologizing -when treated accordingly.)
Minor recurring character Charlton Woodchuck was this on both his major appearances, first convinced he was one of Hollywood's new rising stars despite never having had a single job, and the second time around believing himself to be a genius, visionary director. In both cases he fully expected everyone around him to treat him as thus, and threw major hissyfits when not accommodated. Unfortunately for him, Hollywood and Slappy Squirrel did not share his assessment of his own talents.
Aqua Teen Hunger Force: Master Shake constantly refers to himself in ways that assume whoever he's talking to has heard of him and always believes everything should involve him in some way. He's also a Know-Nothing Know-It-All who's clearly making it up as he goes along, and more clearly thinks he's getting away with it.
Atomic Puppet: Mookie, big time. He was nothing more than a Bumbling Sidekick and The Load to Captain Atomic, and the people of Mega City clearly don't take him seriously, but he believes that he should be venerated by them as the city's greatest superhero, hence his constant attempts to steal the spotlight from Atomic Puppet.
In the episode "The Clock King", Temple Fugate sincerely thinks that the guy who shares his seat at the subway after one year had to know his name, or that Counselor Hill knows his impending legal case simply because his law firm is handling it, or that he gave the Advice Backfire on purpose.
This is also the best way to sum up Riddler's world view in most Batman related media and the animated series is no exception. He claims to be a genius and even smarter than the "World's Greatest Detective" and will go to great lengths to prove it.
Chowder: Mung Daal often thinks that he's the greatest chef around. While his greatness is debatable, he does at least outstrip his rival Endive in actual commitment (Endive values dignity above all else, which leads to methods which seriously abrade Mung "It's not even edible if there's no love" Daal).
Danny Phantom: Appropriately-named Dash Baxter is a slight variation in that only the audience and the main characters see through his self-image, the rest of the characters viewing him exactly as he views himself.
Brian Griffin spent years working on a novel entitled Faster Than The Speed of Love which turned out be a complete rip-off of the Iron Eagle film series, even though Brian claimed he never saw any of them. Everyone who had heard of the book's plot mercilessly taunted Brian about it being a rip-off but he refused to acknowledge it. When the book did get published yet did not sell a single copy after being critically lambasted, the next day Brian read a rave review for a celebrity self-help book and thought self-help books were the reason the novel sold so terribly. He then decided to write a similar book out of spite; the book became popular and Brian slowly began raving "I have created a best selling PHENOMENON" until he was taken down on Real Time with Bill Maher. Brian is also egotistical when it comes to women. Brian always tries to act intelligent and suave to impress women so that he can easily have sex with them, but whenever they break up, Brian tends to blame the women he dates as the reason they broke up instead of admitting that his negative behavior was his own fault. One episode has Brian being confronted by every single woman he ever dated and they all point out how flawed he is, only for Brian to retort with flaws he sees in every woman he dated, saying it's their fault their relationships with him went sour.
Ironically, one episode showed Brian actually does have the ability to be a good writer when he rediscovers an old screenplay he wrote about a single dad who goes back to college to provide for his baby daughter. While initially nagging Lois into reading the script, once Lois actually does she's blown away by how good it is (and spent an entire day trying to determine if Brian plagiarized anything in the script, but found nothing). Unfortunately, when Brian tries to have the screenplay turned into a movie, a bunch of TV executives and James Woods destroy it by turning it into a horrible sitcom about a guy getting into wacky hijinks with his hot co-ed daughter in college (titled "Classholes"). The pilot episode's so bad Joe flies into a rage and tries to beat up Brian.
Quahog Channel 5 news anchor Tom Tucker, who has earned multiple comparisons to Ron Burgundy (and not only due to his Badass Mustache).
"Do you know who I am? I'm Tom Tucker, dammit! I make more in an hour than you make in two hours!"
Miss Turtle from the episode "Mickey vs. Shelby" thinks she's the best parent in the world, but she gets sucked into her own ego to realize that she treats Shelby poorly. So she blames the person watching him.
Goofy became this when he got replace by Von Drake's automatic waitering system, thinking he can do more than be a waiter without any skills.
The aforementioned Gaston is considered by other characters to be a case of this; anyone he interacts with is too sassy to care about his boasts. Case in point:
Inspector Gadget, far more so than in the film version. This actually is a major element which preserves the status quo. Most notably, he is convinced that Dr. Claw is so terrified of him that MAD packs up and leaves as soon as Gadget is assigned to a case. This may be the main reason he canonically can't catch Dr. Claw, despite the number of times they've been physically close: Gadget cannot believe Dr. Claw would dare go near him, and thus cannot recognize him. To some extent, this is also why Inspector Gadget tends to not notice MAD agents trying to kill him or recognize the MAD logo.
The eponymous character is despised by his species due to the combination of this trope and Too Dumb to Live. This is the Irken that singlehandedly shot down the first Operation Impending Doom out of sheer stupidity, and thought that the Tallest would want him assigned to Operation Impending Doom II. The Tallest sent him to Earth simply to get him out of their way (they didn't even know there was a planet there), but he has no idea that it isn't a real assignment.
All Irkens are this trope to some extent, as the Tallest demonstrate. Zim is just notable because he's an incompetent egotist even by their standards; he's basically the worst thing to happen to the Irken Empire, but he thinks he's a war hero.
Jimmy Two-Shoes: Lucius Heinous VII. Sure, he's supposed to be Satan, but he's really not as good as keeping Miseryville, well, miserable as he likes to think he does. The fact that he can't even get one happy-go-lucky kid out of his horns really speaks to that.
This is pretty much Johnny Bravo's defining character. He often admires himself a lot and constantly remarks about how "pretty" he is, as well as his failed attempts at wooing any of the chicks he hits on, who often rebuff his prospects by physically beating on him.
My Life Me: Birch Small especially when it comes to her artworks. She shows off her own "manga art" to her manga idol Miyazaki Lee, which the idol claimed to like only to insult a different "local" comic also made by Birch, which prompts her to bitch him out and start insulting some of the very work of his she was praising earlier.
The Great and Powerful Trixie, who boasts of being capable of doing everything better than everyone. She's an odd case in that she clearly does have a lot of fans (or can at least draw a crowd), but she still manages to be this trope because her ego is just that big.
Done as part of Rainbow Dash's character development. In season 1 she was this trope to it's fullest, but as the show's gone on she's not only Taken A Level In Kindness and humility but also done quite a few acts of heroism to make a name for herself. As of Season 7 The Wonderbolts claimed to have been eagerly waiting for her to join for quite a while, and Dash (for the most part) is more humble: you could call her a Big Name Moderately-High Ego now.
Quack Pack: Kent Powers was presumably based on the original Ted Baxter.
Rainbow Brite: Starlite the talking steed, who likes to introduce himself as "Starlite, the most magnificent horse in the world".
Regular Show: Park Avenue, graffiti artist from "Under The Hood".
Park Avenue: Yes, I am the one who did it! I am the graffiti artist! I fill the world with knowledge! I paint the truth! I paint rebellion! I-
Benson: I'm calling the cops.
Rubberdubbers: Finbar the mighty shark who considers himself to be the most fearsome shark in the sea. Ar ar ar
Rocket Power: Otto Rocket. While he's a highly competent athlete with enough skill of a pro skater, he does tend to overestimate himself very often. The episode "Super Mcvarial 900" is a great example of that.
Samurai Jack: we're introduced to Da Sam'rai in one episode: a flamboyant, rude, and aggressive poser who, to his credit, does manage to take down some Mecha-Mooks with Confusion Fu and dirty fighting before calling out Jack. Jack demands they fight with bamboo and utterly schools him, so Da Sam'rai draws his sword and gets utterly schooled by Jacks' bamboo again. To the man's credit, though, he does man up enough to shove Jack out of harm's way when Aku's minions show up, and gets acknowledged as having potential to be a real samurai for it:
Jack: You have taken your first step to the true path of the samurai.
Season 5 shows that he ultimately gave up on his samurai career and now runs the Bad-Guy Bar where he and Jack crossed paths. He still loves to brag about the experience and thinks the soul-changing encounter is more impressive than the various injuries and mutilations passing bounty hunters had received from Jack.
The High Priestess of the Cult of Aku truly believes that she's a trusted and valued ally of Aku. In reality, Aku only visited her cult once and has largely forgotten about her in the intervening years.
The Simpsons: Kent Brockman is an intentional copy of Ted Baxter. In the episode where Marge stars in "A Street Car Named Desire" musical, the director, while competent, sees himself as this supreme director even though the only play he ever mentions directing was a school play. He prides himself on it though, by carrying the review around and quoting it.
"Play enjoyed by all!"
The Smurfs: Brainy Smurf will brag and moralize to his fellow Smurfs in invariably any situation, only for his advice to be dubious at best and completely wrong at worst. (In the animated series, when one of the Smurfs tires of him, he will be thrown out of the village ...) He believes his quotations (compiled in volumes usually titled "Quotations From Brainy Smurf") will get other Smurfs to see him as a great orator and with insightful wisdom, although the quotes are little more than nonsensical ramblings, or copied wisdom from one of his fellow Smurfs. He thinks of himself as a de facto second-in-command whenever Papa Smurf is gone or needs someone to reinforce his authority, but this authority is often better handled by other Smurfs.
Sonic the Hedgehog (SatAM): Antoine sees himself as a heroic, intelligent "and so very handsome" Freedom Fighter who can take Swatbots in their thousands. In reality he is a sniveling Dirty Coward that often acts as The Load. Sonic and Sally, though much more genuinely competent, frequently have Idiot Ball moments due to their conflicting egos.
Squidward aspires to be an artist, and thinks living next door to idiots like SpongeBob and Patrick while working as a cashier at the Krusty Krab is beneath him. He's not a very good musician, and all his paintings and sculptures seem to be of himself.
Sandy plays with this. She is actually the most intelligent and talented member of Bikini Bottom by far. However this does lead her to overestimate her skills at times and sometimes gets rather overcompetitive and arrogant when someone implies she is isn't the best at something.
South Park: Cartman though he displays a number of tropes at a number of different times. There are also several occasions where Cartman was incognito and openly tried to make his image look better if someone didn't say anything cool about him, even if he had to blow his own cover to do so.
Steven Universe: Peridot. She has referred to herself as "The Great and Lovable Peridot", takes any chance she can get to show of how smart she is, will use her newfound metal powers any chance she gets just to show how great she is, and at one point even referred to herself as the new leader of the Crystal Gems.
Storm Hawks: Finn, whilst a talented sniper, is nowhere near the ladies man he thinks he is.
Sushi Pack: Tako considers himself to be a great artist worthy of the world's admiration, but his abstract paintings are less than admired by anyone, even his own teammates. One episode, in fact, had him chasing down the bad guy not because he stole all the art in the museum, but because he stole all the art in the museum except for Tako's paintings.!
Teen Titans: Control Freak is actually fairly competent as villains go, but the Titans still dont take him seriously due to his goofy personality. He wasn't even mentioned on the list of "villains to watch out for" the Titans East got when they were housesitting the tower!
Ezekiel in World Tour is also one of these, thinking he's going all the way even when Gwen reminds him that he was voted out first last time.
Tyler, who thinks he is the greatest athlete around, but constantly proves to be possibly the worst.
Blaineley has a very high opinion about her TV host abilities that seems unwarranted considering the TDWT Aftermath's reveal she was fired from her old show. She also claims to be extremely famous in her musical number "Blaineriffic", but none of the characters recognize her at all, suggesting she's totally washed-up.
Scott in Revenge of the Island is a Smug Snake who thinks he's a Magnificent Bastard. Lampshaded late in the season when he thinks a trap he put up worked (it was actually Zoey's) and he exclaims, "Hey! One of my traps actually worked!"
Transformers Animated: Henry Masterson, aka the Headmaster is very deliberately a parody of this trope. During the season two finale, Starscream builds a small army of clones of himself, each of whom represents an aspect of his personality and almost all of whom are references to the G1 Seekers. The Thundercracker homage, "Egomaniac Starscream", represents...well, it's in his name. Starscream has a pretty high opinion of himself, but at least he can back it up (to everyone except Megatron).
Dr. Venture. He is a slothful and incompetent "scientist" who has ridden his father's coattails his entire life. He often believe he is the life of the party and highly desirable even when no woman wants to have anything to do with him.
Dermott Fictel, Hank Venture's teen-aged friend, seems incapable of opening his mouth without uttering a conveniently unconfirmable boast. He teaches ninjutsu (actually wears padding and takes hits in a self-defense class), can hot wire a car (except Hank had the keys), can fly a plane (except the Ventures' jet is the wrong class for his license), and is also known as "The Wolf" and/or "Psycho" (to the guys in his old neighborhood who supposedly fought a gang war over the choice). He is also a Know-Nothing Know-It-All, claiming that the Retsyn from Certs mints can be used to make napalm, and a Boisterous Weakling, since the only time we see him actually fight he loses to the show's most notorious wimp.