After watching a film about an alien invasion, Dennis, Curly and Pie Face decide to make their own film. However, Walter stumbles across them filming, and he only sees the action, not the camera. Filming what he sees on his mobile phone, he runs to tell the whole of Beanotown about the alien invasion. As panic spreads, Dennis and his friends discover the chaos and decide to keep filming in order to help make the best of their own alien film. Meanwhile, Sergeant Slipper investigates the alien landing that Walter has seen, and discovers the truth—that the spaceship is a playhouse with glow sticks in it.