In "Out of This World," aired years before Pluto's demotion, the class is rehearsing a play about the solar system where they each play a different planet, but Dorothy Ann is late, so they had to start without her planet... Pluto.
Launcher of a Thousand Ships: Arnold. He's been shipped with everyone - everyone in his class, Ms. Frizzle, Molly Cule, that guy from the hot cocoa episode (Harry Arm), that girl from the water cycle episode (Tiffany), Janet, Azula...
In Israel, the show was just called ‘The Magic Bus’ (because school buses are not as ubiquitous there). Unfortunately, ‘magic’ (or, more accurately, ‘acts of magic’) sounds a lot like ‘drugs’ in Hebrew (קסמים ksamím vs. סמים samím, respectively). Cue many jabs from kids who’ve outgrown the series about the bus adventures being a case of Mushroom Samba.
The episode in the sound museum is also pretty creepy, with the class staying overnight in a vast and seemingly-abandoned building with some very surreal features and chasing after the sound of mysterious music that sounds rather creepy in its own right.
Paranoia Fuel: If you're sick, a science class might enter your body in a shrunken bus to find out why.
Periphery Demographic: The series has gained a large amount of older fans, many of whom grew up with it. It helps that both the facts (for the most part) are still relevant and the characters are interesting. Older fans have been known to revisit the show because of how much they forgot that they had learned in elementary.
That One Level: The platforming minigames in the Explores the Solar System computer game all can be fairly difficult, but the Saturn level with Tim is generally agreed by people who have played the game to be the most frustrating one. The level takes place on tiny slick platforms in Saturn's rings that you will almost constantly be sliding off of into a level-wide Bottomless Pit (causing you to start over) until you get a jetpack a few screens into the level. While the jetpack can keep you from falling into the bottomless pit, it also uses up air. Running out of air will also start you over, without the jetpack, meaning you have to navigate Saturn's icy platforms to get it all over again.