Trivia: In the scene where Lloyd is eating dinner with Harry and they're talking about the pie, Lloyd says "I like it alot" which is a phrase used in the first Dumb and Dumber movie.
Trivia: The guy who plays Lewis in the film also plays a guy called Lewis on the TV sitcom Even Stevens.
Trivia: In the end, we see Lloyd and Harry turn down the Felcher twins. Freda Felcher was mentioned in the scene in Dumb and Dumber where Lloyd and Harry were in the hot tub. Harry was explaining why he was not with her anymore and then we find out at the end of the film that Lloyd hooked up with her.
Trivia: In the scene when the lunch lady is in the school bus, trying to get away from the girl, the truck that pulls out in front of them has "Turbo-Lax" in it, the same laxative Harry put in Lloyd's drink in the first movie.
Trivia: The original writers for this movie were supposed to be Trey Parker and Matt Stone of South Park fame. But they backed out and gave back the 4 million dollars they were paid.
Trivia: In the scene where Harry is going upstairs with Jessica to her room, he falls and tries to trip her, this is something that Lloyd does to Mary Swanson in the first Dumb and Dumber.
Trivia: Just before Harry and Lloyd see the short bus for the first time, they are at the corner of Stan St. and Oliver Ave. This is a reference to the comedy duo, Laurel and Hardy.
Answer: Because Harry and Lloyd had poured gasoline all over the car as well as let the pump keep running when they left. So when the hot ash of the store clerk's cigarette hit the gas fumes, it caused the explosion.
Bishop73