In the banana song scene in Beetlejuice (1988), when Lydia (Winona Ryder) gets up from the table she starts laughing. She can even be heard right in the middle of the scene, and a little later is seen convulsed with laughter.
Was Lydia's reaction in the script or was it Winona Ryder's real reaction to the scene and intentionally left in the final cut?
Lydia was indeed supposed to be delighted by their possession. Here's the bit in the shooting script that details her character's reaction right when they all start dancing:
A look of sheer delight comes across Lydia's face, unlike anything we have previously seen. She dances and claps her hands in time with the music. She is in teen heaven. [...]
Lydia excitedly looks around the room to see if she can see the ghosts. She can't.
So whether Ryder was acting or rather was genuinely amused and used that energy for her character, her jubilant reaction was originally in the script.
