Phoebe was first introduced in the 1987 book, The Magic School Bus Inside the Earth, and Carlos and Keesha were added in the 1994 book, The Magic School Bus In the Time of Dinosaurs.
Phoebe最初登場是1987的書—《 The Magic School Bus Inside the Earth》、而Carlos和Keesha是在1994的書《The Magic School Bus In the Time of Dinosaurs》。