When Howard and Bernadette argue in the bedroom in their Smurf costumes, Howard sets a magazine on the bed. The magazine moves around between shots with no one touching it.
When Leonard picks up the pencil for the holographic experiment, the way he holds it changes between shots.
When Sheldon and Amy are deciding upon which costumes to wear to Stuart's Halloween party, Sheldon asks Amy which kind of tea would she have. To this, she answers Green tea mixed with lemon zinger. In the next scene Sheldon can be seen taking out the first pouch from the box and not having torn it yet. However, in the very next scene, Sheldon is shown putting the tea bag into the cup and pieces of torn pouch can be seen lying on the table.
Amy is extremely excited about a couple's costume. In a previous episode, Sheldon states that Amy doesn't believe in wearing costumes.