Lone Starr and Princess Vespa are sucked into a game of 'Grand Theft Starship', leaving the Spaceballs to conquer the known universe. But, missing Lone Starr's opposition, President Skroob and Dark Helmet follow them into the game world.

Barf is bitten by a chest-bursting alien spider and becomes Spidermawg, just in time to save his home planet from the nasty no good Spaceballs. But President Scroob uses a new weapon to become the super powered Mothball as well.