Just before Rodney takes the city ball express, you can see him standing on a giant cog turning downwards. In the wide shot, the cog above him clearly has a robot on it too, yet when Rodney hops off, the cog above him comes down, and there is no robot to be seen
When Rodney and Fender are pulling the lever, the rooms are located one above the other (i.e., arranged vertically). But during the "armpit farts" sequence, the light in Piper's room is to the left of the building, while Crank's is to the right.
In the board meeting with Ratchet, the small television with Bigweld talking is not visible as the shot pans over the big chair. When we see it from the front, the TV is sitting high enough that it would have been seen from the back.
When Rodney uses Wonder-bot to help his father wash dishes in the kitchen at the diner, his dad has 3 dirty plates already in his "stomach dishwasher". Wonder-bot adds 6 more plates, bringing the total of dirty plates inside dad to 9. Seconds later when Wonder-bot takes the newly cleaned plates out of dad's "stomach", there are only the 6 that were added. The original three are missing.
When Rodney and Fender take the Crosstown Express, the shots of the outside of the ball show it spinning in the air. But in the shot from inside the ball, it's just flying along straight and not spinning.