"Go on, run! There won't be no Yelnats the Fifth!"
"Well that's just TOO DAMN BAD!" Both the timing and the way the line is delivered makes the moment totally priceless.
"Once, there was a magical place where it never rained. The end."
Squid's reaction: "I don't get it."
Mr. Pendanski: "D-I-G, what does that spell?"
Zero: *knocks Pendanski cold with shovel* "Dig!" *runs away*
During a montage in which Stanley becomes accepted by the rest of the campers in the movie, Armpits lifts up his armpits. Everyone runs away from the stink. Trust me, it's funnier than it sounds.
When Mr. Pendanski asks Stanley whose fault it is that Stanley is at Camp Green Lake (obviously intending An Aesop about personal responsibility) and Stanley responds confidently, "My no-good dirty rotten pig-stealing great-great-grandfather!"
Zig-Zag: "Say, I didn't know Marion was a man's name."
Mr. Sir: "It ain't."
The Warden: "Now do as I say." *walks out*
Mr. Pendanski: "What did she say?"
Mr. Sir: "Not much."
Mr. Pendanski: "Then what do we do?"
Mr. Sir: "You do as I say." *walks out*
Mr. Pendanski: "But you didn't say anything either!"
When Armpit tries to give the warden a knob he found and gets his weekly shower tokens taken away, who's more upset about this? His cabin mates.
Squid: Man, you sleepin' outside!
When Stanley arrives at the camp, he's not too happy to be assigned a cot that previously belonged to someone nicknamed "Barf Bag".
Magnet: This was Barf Bag's bed.
[Shot of urine stain]
Mr. Pendanski: [Offscreen] Keep your bed clean!
When Stanley IV is sentenced:
Judge: "Arise, Stanley Yelnats."
All three living Stanleys stand up.
Judge:(rolls his eyes) "Stanley Yelnats the Fourth."
Stanley II and Stanley III sit down.
At the end of the movie we have a particularly silly Funny Background Event; Twitch, a hyperactive boy who got his name because he twitches whenever he sees or hears about a cool car (and indeed, was arrested for trying to steal one) had replaced Zero and Stanley after they left. At the end of the movie, when Stanley is leaving in a limo, you can see Twitch running after the limo excitedly before Armpit holds him back.
Mr. Sir's obsession with talking about how horrible girl scouts are. Becomes a Brick Jokewhen Camp Greenlake was converted to a girl scout camp at the end.