Dennis' gang decide to make their own alien film. When Walter stumbles across them filming, he's convinced there is an alien invasion and raises a red alert in Beanotown.
The joke shop owner, Mr Har Har, needs Dennis's help to persuade his mother not to close the joke shop down. The gang decides to try to pass Mr Har Har off as a successful vet.
Dad agrees to buy Dennis the best skateboard there is if he can win a prize at the upcoming school award ceremony. The only prize that Dennis can try to win is the best behaviour prize, so he does everything he can to win the contest.
Mum is going to the yoga school and leaves Dad in charge. During her absence, Dennis, Curly and Pie Face try to make a pie, with disastrous results to follow.
After a wrestling accident, Gnasher swallows a canister of laughing gas at the vet's. Dennis, along with Gnasher hide in the conference centre, where dad gives a speech. However, the canister leaks, causing Gnasher to fart laughing gas and having everyone laughing.
On a school trip, Dennis finds out that he is descentant to a warrior tribe. He also discovers that Montanna Smith (a famous Indiana Jones-esque explorer and one of Walter's personal heroes) is actually a thief who's trying to steal the treasure of Dennis' ancestor.
