Leonard and Thrash are first seen taking out the trash for Calvin Wheeler after how he paid them with concert tickets last time; much to Calvin's parents' disapproval since they actually asked him to take out the trash instead.
A few days later, after Calvin gets a Labrador/Saint Bernard hybrid dog named Tyco, Leonard and Thrash have been paid by a stuck-up, rich kid named Preston Price to make Calvin and Tyco stay away from the dog show and encourage him to drop out even if Calvin promises to take Tyco back to the pound after school after all the trouble he caused him the other day. Luckily, Tyco breaks free from and with the tree he is tied to on a leash by Calvin, breaks through the fence, and rescues Calvin from the two would-be trouble makers. This rescue later changes Calvin's mind about the pound and allows Tyco to stay. Leonard and Thrash lie on the ground defeated and aren't seen throughout the rest of the movie after that.
Leonard and Thrash about to beat Calvin up (failed)
Leonard about to punch Calvin (failed)
Leonard and Thrash surprised and scared by Tyco's presence
Thrash screaming because of the tree heading his way