Revealing mistake: When Andy is hit by the baseball bat by Chucky you can see that the bat doesn't make contact with him. (01:11:20)
Revealing mistake: When Chucky follows Andy home and drops from the chimney and kicks the cover off, its obvious that this isn't Chucky and its a real person dressed as Chucky.
Revealing mistake: In the scene where Andy's aunt is sitting on the couch and Chucky runs by, look closely, you can see it's not Chucky but it is a person. (00:19:35)
Revealing mistake: When Mike is in the car being attacked by Chucky, after he hits a metal can and makes sparks, he swerves violently in the road, and on the road you can see several pairs of dark skidmarks in the exact same place as he swerves, obviously from previous takes. (00:55:15)
Revealing mistake: Look very closely at the way Maggie is knocked backwards after being struck with the hammer. It seems as if she is deliberately throwing herself backwards, which also means they may have used reversed footage.
Answer: When he jumps out, he screams a generic "Ahhh!" and then quickly shouts "Surprise!"
TedStixon