The Hover Bike is a vehicle invented by Professor Frink.
Frink asks Bart to test it out but he refuses due to there being wet cement up ahead, which he wanted to vandalise. Even though he tells Bart it is a once in a life time opportunity, he still refuses. Later, Frink comes to Bart on the Hover Bike telling him that he bets he wishes he took the chance now.
The bike returns in The Simpsons: Hit and Run where it is a playable car. You can purchase it for 1000 coins after the 7th level.