In the scene where Will burns down the kitchen via "flambe", you can clearly see a fire extinguisher on the counter behind Will when he walks into the kitchen. However, after Will starts the fire, it disappears.
When Geoffrey brings the tray with iced tea into the living room, the tray disappears between shots.
Obvious dummy when Carlton is thrown out of the VW bus. Most noticeably, the legs are much longer than Carlton's.