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!
Arnold: Why oh why do we always wind up in long, dark, slippery tubes? Ms. Frizzle: Oh, we're just lucky I guess, Arnold.
"Goes to Seed" where the class goes to Phoebe's old school to fetch her plant for the magazine photo. The building is actually called Phoebe's Old School!
Actually, it's called so only in her Imagine Spot. Still kinda funny, though.
How Phoebe, fearing embarrassment, is desperate to keep the class hidden from her old teacher Mr. Seedplot.
Arnold: Gee, maybe you should've stayed home today, Phoebe.
"In the Haunted House": The "ploopy" sound effects from Carlos' instrument.
"Gets Lost in Space" gives us a funny little Funny Background Event with the skeleton covering his 'ears' from Janet's bragging. Clearly he finds her annoying like the rest of us...
"Gets Ants in Its Pants": Keisha leads an ant into the classroom, which Liz naturally tries to eat. While the ant is climbing around on the camera, towards Liz, Liz holds her mouth open and her tongue out, to try and get the ant to crawl inside. The ant just crawls onto her tongue, up her cheek, and over her head.