The Tired Turtle Express is an early elementary piece from the book "Comics & Card Tricks: 12 elementary piano solos", by Christine Donkin. I had so much fun practicing this one: first time I encountered a piece with ritardando, first time practicing grace notes, and the first time playing something a bit more jazz-y!
Sheet music for this piece:
Book Piano Pieces Vol. 1: Elementary (a collection of three books in one volume)