Lone Starr needs a million Starbucks to pay Vinnie protection money. Vespa wants a million Starbucks to buy matching his and hers space-jets. So Vespa enters the Druidian Idol singing competition as 'Vespacia' and Barf as 'Kelly Barfson'. But President Scroob, anticipating their presence, uses a brain-zapper to turn the entire audience into mindless killers.
Lone Starr and Barf are named fans of the day at a Spankees ball game and win a trip to Watch your Assic Park to see the Spankees train. After they arrive at Isla Nueblo (180 star miles from Planet Costa Rica) they learn how Skroob, the owner of the Spankees, uses a combination of steroids and dinosaur DNA to create Dino-athletes and rule the sports universe. Despite being quite disgusted, Lone Starr, Barf, Vespa and Dot take the park tour anyway, accompanied by Skroob's precocious 9 year old niece Jasmine and two anonymous lawyers.
Years ago Lonestarr's father stole the One Onion ring from Scroob's father. When Barf finds the Onion Ring stuck in an old couch inside the Eagle 5, Yogurt sends him on a quest to throw the Onion Ring into the deep fryer of Lardor. Meanwhile Skroob orders Dark Helmet to build him a dark army. Unfortunately they end up with a dork army instead.