I understand he gives a pass on characters he didn’t actually write, like Blade and Ghost Rider, and his bit in Guardians of the Galaxy was cut (He was supposed to be in the post-credits scene with Howard the Duck and Warlock’s cocoon, giving the finger to the Collector, but they decided that might be too much bird-flipping for one movie). Anyway, it’s more of a tradition than an obligation.
Elmo Lincoln was the first movie Tarzan, and had bit parts in Tarzan’s New York Adventure (starring Johnny Weismuller) and Tarzan’s Magic Fountain (starring Lex Barker).
Tom Conway appeared in Tarzan’s Secret Treasure as Medford, and Tarzan and the She Devil as Fidel.
Michael Parks was Earl McGraw in Kill Bill Vol 1 and Esteban Vihaio in Kill Bill Vol 2
He was also Earl McGraw in From Dusk Til Dawn, and both Grindhouse movies (Roadhouse, Planet Terror)
Terry O’Quinn played 3 different characters on The X-Files:
- Lt. Brian Tillman in the episode Aubrey
- “Shadow Man” in the episode Trust No 1
- Special Agent Michaud in the first X-Files movie.
Jock Mahoney played a villain in Tarzan the Magnificent, then played Tarzan himself in Tarzan Goes to India and Tarzan’s Three Challenges.
Since most studios had contract players, it was pretty common in the 30s and 40s for actors in series to play different roles in the series.
For instance, for Charlie Chan movies:
Francis Ford played different characters in three different Charlie Chan movies.
Frank Conroy was in two Charlie Chan movies, as different characters
Thomas Beck was in four Chan movies.
Marc Lawrence was in three (possibly four) of them
Eddie Collins was in three (two of the names are similar, but not the same)
Well, there’s Burt “Cato” Kwouk too (as Mr. Ling in “Goldfinger” and Spectre #3 in “You Only Live Twice”).
He also played a Romulan in ST:TOS “Balance of Terror.” He returned as Sarek on ST:TAS “Yesteryear” and then again twice, I think, on ST:TNG.
René Auberjonois played a Starfleet officer in ST:TUC and Odo on ST: DS9.
Ummmmm, is there any reason to think that they weren’t supposed to be the exact same character in both movies?!? Because I always thought they were obviously meant to be! 
Ronald Lacey qualifies, too. He played Toht in Raiders (the guy who grabbed the medallion barehanded), and a member of the Gestapo in Last Crusade.
I know the OP specified no TV shows, but someone’s gonna hijack this thread eventually and it may as well be me.
In season one The Sopranos, Drea de Matteo had a brief role as a restaurant hostess (the scene where Dr. Melfi is told her table won’t be ready for hours, until Tony Soprano walks in and arranges for her to get seated immediately.) The producers liked her so much, she was subsequently cast as Christopher’s girlfriend Adriana La Cerva – though one could argue that she was the same character in both roles.
Also in The Sopranos, Joseph R. Gannascoli played a minor role as a pastry shop customer (he’s the guy Christopher told to get lost shortly before shooting the clerk in the foot.) In subsequent seasons he was cast as gay mafia hitman Vito Spatafore, a clearly different character.
In Married…With Children, Dan Tullis Jr. often appeared as a generic law enforcement officer, including an FBI agent who was tracking Steve Rhoades after he’d stolen an endangered owl egg. By season eight his character was codified into Officer Dan, a charter member of NO MA’AM.
In Game of Thrones, King Tommen Baratheon was portrayed in seasons 4-5 by Dean-Charles Chapman, who previously had a small role in a prior season as a young Lannister prince who gets kidnapped & murdered. (Ironically, in earlier seasons, Tommen was played by a completely different actor.)
Odd coincidence, I was watching Rollerball just as I read that. Kwouk is the doctor trying to get Jonathon to sign the papers to turn off Moonpie’s life support.
Which brings us to Shane Rimmer, he was uncredited in You Only Live Twice, Diamonds Are Forever, and Live and Let Die, and finally a submarine commander in The Spy Who Loved Me.
For TV shows, it’d be tough to beat Jack Garner; he was in 26 episodes of The Rockford Files playing at least a dozen different characters.
Hail Ants, in this article, Bruce Spence specifically says that the two characters were similar but definitely not the same person:
Maggie Smith as Nurse Bowers in Death on the Nile and Daphne Castle in **Evil Under the Sun. **
Jane Birkin as Louise Bourget in Death on the Nile and Christine Redfern in Evil Under the Sun.
Can we include an actor playing multiple different characters in the same movie?
For example, Peter Sellers played Captain Mandrake, President Muffley and Dr. Strangelove (all main characters) in “Dr. Strangelove”.
Sellers was a slacker: Kind Hearts and Coronets - Wikipedia
Reminded me of another, Graham Stark:
Hercule LaJoy in A Shot in the Dark
Pepi in Return of the Pink Panther
Two hotel clerks in The Pink Panther Strikes Again
Dr. Auguste Balls in Return of the Pink Panther
Hercule Lajoy (again) in Trail of the Pink Panther
A bored waiter in Curse of the Pink Panther
Professor Auguste Balls (again) in Son of the Pink Panther
And if we allow for trick photography, Buster Keaton played an entire theater full of people (projectionist, on-stage performers, audience members, the orchestra, on-screen movie actors and IIRC even a performing monkey) in “Sherlock Junior”.
At one point one of the characters (played by Keaton) says to another (also played by Keaton) something along the lines of “This fellow Keaton is certainly the whole show!”.
Minor correction: Keaton did this in “The Playhouse.” The most amazing thing about it all? The camera was hand cranked.
D’oh! Yes, quite correct. I have both movies at home, misremembered the name.