At the end of the traffic jam episode, Malcolm goes on about how great it was an how they should do it again. During his dialogue, there is a shot of Lois looking out of the window and in the background, Malcolm can also be seen looking out of his window saying nothing, although his voice can still be heard (Widescreen version only, this does not happen in the 4:3 format).
In the preamble, Dewey (to the left of and in front of) talks to a scarecrow. In the long shot (with his voice) Dewey is nowhere to be seen.
Near the end of the episode Lois smashes a window to release a dog from a car, leaving a small row of glass at the bottom of the window, when the shot pulls away as the dog jumps out of the window the small row of glass at the bottom is gone.
During Dewey's car journey (second view) sometimes his shoulders are (inexplicabably) in bright sunlight and sometimes in shadow.
For most scenes at the crash site the road is in full sunlight but in Hal's exchange with the motorbike cop, the road is in shadow.
When "Reese" jumps on the roof of the ice cream truck the stunt double is clearly an adult with bigger shoulders and thicker arms & legs than Reese has.
When "Reese" rams his head into the door of the ice cream truck the stunt double is clearly an adult with bigger shoulders and thicker arms & legs than Reese has.
When Hal lets the other car pass after it gets hit you can see the tire mark from a previous take when Hal slams on the brake and swerves to the right.
After the INS van is seen, then Dewey is seen inside the van, there is a shot of a white limo going through traffic lights. This image is reversed. The signs on all the stores are backwards.
When the family arrives home and Dewey is outside, Malcolm bumps into Lois. You can clearly tell it is a legit mistake as Malcolm is not looking where he is going. You can quickly see he shakes his head slightly and runs off.
Instead of waiting for police to come and block whole road, they could have drove past the wreck and be on their way home.