Randy's Ninja responsibilities drive a wedge between him and Howard during their rehearsals for Norrisville's Battle of the Bands, leaving Randy to figure out a way to balance his Ninja duties with being Howard's friend.

When a real monster disrupts Norrisville High's annual practice Monster Drill, Randy must retrieve his Ninja mask and the NinjaNomicon in order to save entire school.

Randy and Howard join their school's "Wave Slayer" team but as jet ski waxers. When Randy accidently damages the jet ski belonging to the team captain, Buttermaker, moments before their biggest race, he and Howard must step up and find a way to save the race.