Continuity mistake: At the very end when the Munroe family gets stopped by the police, they walk directly behind the RV. A moment later when the RV rolls down the hill (and runs over the police car) it is facing toward them. For it to do this it would have to run over them.
Other mistake: In the scene where Bob is trying to get reception on his pocket PC, he is on a rock and the pocket PC beeps, indicating that there is no signal. But when it goes to a closeup of the pocket PC, you can see in the top left hand corner that the signal is full.
Continuity mistake: In the RV, Jamie puts stacks of dishes away in the overhead cabinet - second from right, when Cassie moves Carl off the couch. When Bob makes the sharp right turn, the dishes pour out of the overhead cabinets, but the ones that come out of the second cabinet are not the same dishes that Jamie put away. (00:12:20 - 00:15:00)Super Grover
Continuity mistake: When Earl gives Cassie the list of places that sell organic health food, in the close-up she holds the papers with her right hand at the top and left hand at the bottom. However, in the next shot it's the opposite way, her right hand is at the bottom and left at the top. (00:44:05)Super Grover
Revealing mistake: When Bob is riding the pushbike down the steep hill to get to his family and the Gornickes at the bottom, in some shots you can blatantly tell that a stunt double that looks nothing like Robin Williams is riding the bike. The stuntman is also visible later when Bob is on the roof of the Gornickes' bus.
Continuity mistake: Just forward of the right rear wheelwell, a small dent disappears and reappears throughout the movie.
Factual error: There is no way Bob would manage to get the RV as stuck as it was going up the Diablo road. Just as the top of the road had made contact with the undercarriage the RV would have stopped moving.
Deliberate mistake: At the end, there is no way that the RV managed to roll over and flatten the vehicles in its path.
Continuity mistake: When they arrive at a campsite to take in the view of the lake that Bob saw with his family as a kid they leave the door to the RV open with the stairs down. After some dialogue the RV rolls into the lake with the stairs up and the door closed.
Continuity mistake: After Bob comes home with the RV, when he and Jamie walk into the kitchen there is a butcher block cutting board laden with items, at the edge of the counter. However, when they speak beside that island counter the cutting board is gone. (Even more noticeable on fullscreen DVD.) (00:10:20)Super Grover
Visible crew/equipment: After Bob urges Alpine not to merge, when Carl flips Todd there is a huge straight edge shadow where they stand, however, there is absolutely nothing near the seated people that would cause such a shadow - only the crew's equipment. (Even more noticeable on fullscreen DVD.) (01:29:20)Super Grover