Zack's Alligator Goes to School, by Shirley Mozelle and pictures by James Watt.
I can read! Level 2: Grades 1-3; High-interest stories for developing readers. This is a sequel to the Zack's Alligator Book where Zack receives an alligator.
"Show-and-tell surprise: "It's just a dumb key chain!" Buster says when Zack brings his alligator to school for show-and-tell. But Bridget is no ordinary key chain. When she falls into the aquarium, she grows to full size! Whirling, dancing, and singing, the zany girl 'gator turns the classroom upside down. Show-and-tell will never be the same again!"