From the Super Mario Wiki
Mona's scooter is a motor scooter constructed by Dr. Crygor for Mona. It appears throughout the WarioWare series and is Mona's primary way of getting around. During her various part-time jobs, she uses her scooter to drive from one place to another, and also manages to escape from her pursuers such as the Dinosaurs. In WarioWare, Inc.: Mega Microgame$!, Mona's Elephant, Pig and Monkey were inside of the scooter and popped out by pressing a button on the handlebar.