Other mistake: Chucky emerges from the fireplace, engulfed in flames, walks to the couch and is seen crawling on the couch before falling to the floor and burning on the floor. And yet nothing else catches fire, and the few tiny flames that do drop, like on the corner of the wooden table, don't spread and put themselves out.
Other mistake: When Karen is fighting Chucky for the first time, she's holding him, but also pushing him away. At one point he's about arm's length away and she moves her hands so she's not holding him and he's not holding her, but he doesn't fall. In the next shot, his legs are up against Karen's body.
Answer: When he jumps out, he screams a generic "Ahhh!" and then quickly shouts "Surprise!"
TedStixon