Rookie is a boss appearing in Mario & Luigi: Superstar Saga. He is actually Bowser who lost his memory after being shot out of a cannon. He is found by the Shadow thief Popple, who makes him his partner. After being flung off the Beanstar he remembers who he really is.
Rookie attacks by throwing hammers at the Mario Bros. who can repel it with a hammer strike of their own. He throws two, faster moving hammers when they attack Popple. He can also shoot Bowser's traditional flames.
When fought in Hoohooniversity he has the same attacks.