Adam Westing: Done hilariously in The Simpsons season 13 episode "I Am Furious (Yellow)", where he plays a somewhat crazy version of himself. He won't leave Comic Book Guy's shop, breaks a toy Batmobile in an attempt to fit The Thing inside it, and even believes that he can turn into the Incredible Hulk.
Alliterative Name: Peter Parker, Bruce Banner, Reed Richards, Matt Murdock... the list goes on. Justified, in that Stan was working on more than a dozen comics at any given time when he created those names, and the alliteration served as a mnemonic. Sometimes it didn't work, which is why the Hulk's full name is "Robert Bruce Banner" (one issue called him "Bob Banner" over and over), and why an early issue of Amazing Spider-Man listed Peter Parker as "Peter Palmer". This was parodied in an episode of The Big Bang Theory.
He even had this in real life with his brother Larry Lieber.
He also ended up giving his co-workers alliterative nicknames — in addition to his own "Smilin' Stan," there was "Jazzin' Johnny Romita," "Adorable Artie Simek," and others.
In Heroman, Stan appears as a patron in the restaurant Joey works at who's always drinking coffee.
He originally created J. Jonah Jameson so there would be a character he could play in an adaptation, which ended up never happening despite the numerous adaptations featuring him (and hey, J.K. Simmons played such a good JJJ).
Comic Book Time: Lee was in charge when Marvel first began to abandon its real-time storytelling in favor of "Marvel time" in 1968. The statement that comics do not represent change, but "the illusion of change" is usually attributed to either him or Marv Wolfman.
He has contractually-obliged cameos in almost every movie based on one of his works, and usually appears in Marvel movies he isn't contractually obliged to get cameos in. As for his cameos:
Spider-Man Trilogy: In 1, a heroic bystander who saves a kid from falling debris. In 2, another bystander. In 3, a bystander who poetically muses about Spider-Man to Peter in the beginning.
Hulk: A security guard getting into an elevator with Lou Ferrigno.
The Incredible Hulk: The civilian who is poisoned by Bruce Banner's irradiated blood in the beginning. Considering how his The Simpsons persona is a Cloud Cuckoolander who thinks he can actually turn into Hulk like described below, it's amusing to think him actually doing so in the movie as well.
Daredevil: A man reading a newspaper who almost walks out into traffic only to be stopped by the blind kid Matt Murdock.
Fantastic Four: Willie Lumpkin, the Baxter Building's mailman. In Rise of the Silver Surfer he plays himself trying to get into the wedding, a Call Back to the same thing in the actual comics.
Iron Man: He plays a person who was mistaken for Hugh Hefner by Tony. In Iron Man 2 he is mistaken for Larry King. Whether he is actually supposed to be these people is unknown. And in Iron Man 3 he appears in a blink and you'll miss it moment as the judge for the Beauty Contest on one of the screens in the news van that Tony temporarily hijacks.
Thor: He plays a New Mexico local with a truck trying to pull Mjolnir from its spot. Credited as Stan the Man.
Captain America: The First Avenger: He plays an Army general in a crowd who loses the opportunity to see Rogers because he left on another mission, but mistakes the messenger for Capt. "I thought he'd be taller." This is a semi-exception as, while Lee didn't create the character, he did serve as Timely Comics' editor during the Golden Age, not to mention introducing Cap to the Silver Age and creating Cap's trademark move of throwing his shield.
X-Men: In the first film, he appears as a random beachgoer who watches Senator Kelly emerging from the ocean. In X-Men: The Last Stand, he appears in the beginning of the film as a neighbor of a young Jean Grey watering his lawn (a scene in which fellow X-Men writer Chris Claremont also cameos). As an aside, he couldn't make a cameo in The Wolverine because of the film's overseas filming in Australia and Japan and deliberately sacrificed a cameo in X-Men: Days of Future Past (filmed in Montreal, Canada) for attendance at Fan Expo 2013 at Toronto, Canada.
The Avengers: Near the end of the film, Stan shows up as a man playing chess in the park, who is interviewed by a news crew regarding the events of the movie's finale. His character believes it all to be a hoax. He also pops up in one of the deleted scenes as a guy at a cafe who alerts Cap to the waitress's interest.
The Amazing Spider-Man: During Spidey and the Lizard's fight, he plays an oblivious librarian who listens to classical music with noise-cancellation headphones while the fight goes on behind him. He reprises the cameo in How It Should Have Ended'sepisode on the moviewhere he blames the Avengers for the mess and warns them he's got his eyes on them.
He appears as himself in the series finale of Spider-Man: The Animated Series when Madame Web brings together several Spider-Mans from alternate universes, one of whom is an actor who plays him in the real world. His wife Joan Lee voiced Madame Web, and the animated Stan asks, "Who is that exotic woman?" when he sees her.
Historical Villain Upgrade: Frequently gets this from partisans of co-creators like Jack Kirby and Steve Ditko — though admittedly he's never been good at sharing credit (then again, neither were Kirby and Ditko).
Hoist by His Own Petard: Inverted — he caused this with an anti-drug comic (commissioned by the US Government) that The Comics Code Authority refused to approve due to arcane language that did not permit any portrayal of drugs, whether positive or negative. He ran it anyway, and the CCA ended up looking like idiots. The CCA very quickly rewrote the Code to allow negative or cautionary portrayals of drug use, inadvertently helping to usher in the Bronze Age Of Comic Books. More than likely as a result, the influence of the Code itself began to wane in the following decades (eventually leading Marvel — among other companies — to abandon it altogether).
In Case You Forgot Who Wrote It: "Stan Lee Presents" appeared on all Marvel issue titles for decades (because he was Marvel's publisher at that time, though not a writer except for the occasional special project).
Jerkass: Stan often portrays himself as a bit of a Jerkass in comics where "Stan Lee" is a character. Stan has also said (presumably at least somewhat in jest) that he based legendary jerkass J. Jonah Jameson on himself, or at least the way he thought comics readers imagined him. He was also kind of crusty when he appeared on The Big Bang Theory (then again, Sheldon did show up at his house and promptly went inside of it without his permission).
Taken to its logical conclusion where he's the Big Bad of Ultimo.
And then there's his role as "principal Stanley" in Mini Marvels, where once Spidey starts angsting — justifiably — about his status as a Butt Monkey, causes Stan to look awkward once he mentions "who decided this to happen to me?".
Ascends in X-Play, where "Roger the Stan Lee Experience" recounts tales of doing Jack Kirby's wife and stealing credit for Kirby's success.
Also happens in his guest spot on Chuck - where it's implied that his whole career has been some sort of CIA operation.
Stan: (After seeing Homer go on a minor rampage where he coincidentally got green paint all over him) He's not the Incredible Hulk! I'M the Incredible Hulk! (Yells and tries to Hulk Out) C'mon change dammit! Grrr, I did it once before!
"Comic Book Guy": Oh, please; you couldn't turn into Bill Bixby...
Take That: In his Just Imagine series, he makes Robin a bad guy. Knowing how he hates sidekicks, doing that to the character that popularized comic book sidekicks would seem more like this than just trying to make him a complex character.
In his recent colab with How It Should Have Ended, he gave his views on how certain films should've ended. He then shows three more, each showing him interrupt George Lucas while he's writing each of the Star Wars prequels, then tossing the script of each into the fireplace.
Villain Decay: While his heroes and writing style are still iconic today, his storytelling style is also somewhat infamous for really introducing a lot of this to Marvel villains — he'd have them say things like "This time my brilliant plan will destroy those meddling heroes!!!" without any sense of irony, even after the villain listed all the times they'd already gotten stomped. In the early 1960s, it still kind of worked; by 1969 or so, not so much. Much of his own later work — not to mention a great deal of comicry that followed in his footsteps — had to spend time fighting the villainous cliches he himself constructed.