As the police in the car start to chase Charlie and Marshall on their own police bike, the driver pulls up the CB mic twice to call in for backup.
When the two crooks get "switched" on the train. It cuts to an exterior showing a train with only 1 engine (F40PH), but when they boarded the train, the power consist was 2 engines (back to back F40PH's), and when the train stops at the station, it again has 2 engines.
When Sam is about to kiss Marshall in Charlie's body, Charlie in Marshall's body quickly comes in , then Sam kisses Marshall in the forehead and leaves a big horizontal mark, then when she says "Goodnight my favorite men", the camera comes back to Marshall and he has a little inclined kiss mark, instead of a big horizontal one.
When Judge Reinhold is playing the video game on Atari, he is eventually interrupted by someone. He is then seen talking to this person, but in the background, you can clearly see the game continuing to play even though no one is operating the controller.
When Marshall goes through the revolving door into the office building, the sound level from the instruments of the carol players outside remains the same. It doesn't fade until after conversations begin.
When Marshall pulls Charlie into the limo, you can see the camera reflected on it.
When Marshall is in his taxi, going to his building, you can see the boom mic reflected on the window of the taxi when he opens the car door.