Continuity mistake: After Ralph destroys the cake and it goes all over the place, we cut to a wide shot. In this shot, to Gene's right, there is a small amount of cake on the floor. In the following shot, the amount of cake has doubled. Also after Ralph destroys the cake Mary is holding the people that were on top of the cake even though Ralph just destroyed them. (00:13:10)
Other mistake: During the cast in the credits, 1st Commercial Guy is misspelled. They put "1st Commerical Guy."
Continuity mistake: At the end of the movie, before the Guardians leave, Jamie rushes over to hug Jack. In the first shot, the top of his head nearly reaches Jack's ribcage. However, in the following close-up shot, Jamie is almost at the same height as Jack's shoulders. (01:27:30)
Visible crew/equipment: When Fred is carried on to the Camp Iwannapeepee bus and the doors close, a camera tripod and crew member are reflected in the door windows. (00:08:57)