Stephen Root in Office Space. His bits as Milton Waddams lifted an amusing movie into the hilarious realm.
Leonard Nimoy in THEM!. He has a walk-on and speaking role as a U.S. Army SSgt. in an inter-service communications center.
Marlon Brando got first billing on Superman: The Motion Picture, a movie he was barely in.
Meh, is the Rodian-to-Latin alphabet transcription that standardized? 
Though I’d argue that role is more influential as an example of a big name actor accepting a role they thought was beneath them and being a total dick to to everyone as a result, rather than anything the character did on screen.
If that character doesn’t choose to rocket a baby to Earth, there’s no movie; and no sequel, if he doesn’t get Zod (a) sentenced to the Phantom Zone while (b) swearing vengeance on The House Of El.
Yeah, I was working commission sales at the time, and we threw lines from that scene around a fair bit, jokingly of course. We could be intense, but never Alec Baldwin intense.
Though I meant culturally.influence not influencing the plot of the movie (most movies have minor characters that influence the plot). And as cultural phenomenon that role, if it is known at all, is known for Brando’s prima Donna attitude on set.
It was also Brando’s idea to have the S crest on Superman’s outfit be the family crest of the House of El, which has since permeated into the modern DC movies and, AFAIK, the comics canon as well.
The only role quoted, in its entirety, in the AFI’s 100 years…100 movie quotes.
“Terminate with extreme prejudice.” From Apocalypse Now, of course. It is that guy’s only line in the movie.
This is what I came in here to say. I think it’s the best example in the thread.
Is Brig. Gen. Jack D Ripper really that minor? He’s basically the bad guy throughout most of the movie movie, isn’t he? I’ve not seen recently but I remember him being a major character not a minor one.
Indeed, he definitely was not a minor character. Mea culpa. In my defense, at that time in the thread, I was confused and thought we were looking for small bits of dialogue or quotes that were influential and/or memorable.
Sebastian Shaw has only two lines in Return of the Jedi.
What about this little fella? no lines at all and barely does anything except jump, grab hold of someone and then die a bit later.
Ah though that is the opposite of the Monty Python situation, as he’s playing a major character who appears throughout as one actor (David Prowse) and has a ton of dialog voiced by another (James Earl Jones). So I don’t think it counts.
Not a speaking role, so I think by SAG-AFRA rules not a character 
Well that is just nitpicking 
But at the point he’s no longer Darth Vader but Anakin Skywalker once again. That’s how he’s identified in the script.