|“||True. Sometimes a new species can be a problem, but not always. Honeybees were new to North America once. But they became part of a new balance. No disasters, at all, just yummy honey.||”|
—Valerie to Arnold
The class welcome Jyoti, the new student in Valerie Frizzle's science class. But then an unexpected visitor stirs up concern, and especially Arnold is worried especially when he isn't used to changes. When they find out Valerie is gone, looks like Arnold is the odd-one-out. They visit the Galapagos Islands, and Arnold gets the bad idea- he leaves Fiona's special Magical Crazy-Growing Must-Stay-in-a-Pot Crescit Leiunium Frizzlaeia Vine in the island, which causes a huge prickly problem. When they go back in time to stop it, Arnold learns that his new teacher might not be a bad invader to his class's ecosystem.
- Phoebe went back to her old school and Jyoti took her seat.
- This is the only episode when Fiona Frizzle gets sad.