It's a movie, but when Sigourney Weaver's character says "Well, fuck that." and it's edited to say "Well, screw that." without changing how her mouth moves at all is about the funniest one I can think of.
Some of those cut scenes are present on the DVD release. There's one where Weaver's character does a bit of a strip tease to disteact some aliens (the modification to her outfit is still in the movie, it just changes randomly between scenes) and another where Shalhoub's character is explicitely confirmed to be high off his ass the entire movie.
!bmoviebonanza@lemmy.world has links to #Monsterdon, a weekly watch party over on Mastodon. Galaxy Quest might be a bit too well made for their usual brand of movie, though.