Funny / The Magic School Bus
Pretty much any time Carlos makes an Incredibly Lame Pun, followed by everybody else yelling "CARLOS!".
Ralphie's robot misinterpreting the term "Cool it" in "Flexes Its Muscles".
Arnold dinging in "Makes a Rainbow". It Makes Sense in Context, we promise.
From Inside Ralphie, Liz tries the standard shake him, and "use an alarm clock" tactics to wake up Ralphie to no avail. Her next method: using a GONG!
From "The Busasaurus":
Before that, the T.Rex tries to tip the bus (which looks like a dinosaur) over to eat it. The kids panic, but Ms. Frizzle just casually looks over her insurance manual without a care in the world.
Arnold Stating the Simple Solution to DA losing her books in Blows Its Top.
Arnold: Wouldn't it be easier to go to a book store?
Phoebe's old school is actually labelled as such on screen.
Pretty much any time the baker (voiced by Dom De Luise) appears onscreen in "Gets Ready, Set, Dough."
Baker: NO!! NO, I'M NOT CRAZY!! Perhaps my establishment just happens to attract a higher breed of moth, that's all.
Want to sum up the show in two lines?
Arnold: As long as we don't get blasted, roasted, toasted, or eaten, I'm happy.
Ms. Frizzle: Oh don't worry Arnold. That's not until next week.
When the class think the monster in Walker Lake ate Wanda.
While Arnold is in disbelief over the fact that he just went on a completely, normal, mundane, commonplace field trip to the zoo, Tim agrees and theorizes that seeing wild animals would have been much weirder if they, oh, saw them wandering around the city or something...
Tim: Can you picture that?
Ms. Frizzle: Absolutely, Tim! We can all feature wild creatures!
Arnold: What?! Tim, quick — take it back!
In "Cracks a Yolk":
Arnold: Why oh why do we always wind up in long, dark, slippery tubes?
Ms. Frizzle: Oh, we're just lucky I guess, Arnold.