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.
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.