Factual error: The movie appears to take place in the winter but when Andy goes into his mom's room with breakfast at 6:30 in the morning it is light outside. At that time of the day it would still be dark outside.
Continuity mistake: When Andy makes his mother breakfast in bed he brings in a glass of orange juice but over the course of the scene of him and his mother talking it changes to a much lighter colour. It could have been switched with a glass of milk or cloudy lemonade but it's probably just the same orange juice that's been watered down over multiple takes.
Answer: When he jumps out, he screams a generic "Ahhh!" and then quickly shouts "Surprise!"
TedStixon