Revealing mistake: During the dance number in the airport, Santa grabs a security guard who then starts break dancing. It's obvious this dancer is a stunt double as he's younger and skinnier than the real guard.
Other mistake: At the beginning, Jack reveals that he has lots of food allergies and asks the bartender to prepare his shake lactose free, implying that he is allergic to dairy. But later he eats a snowman cookie that Mrs. Claus reveals has butter in it.
Suggested correction: Being lactose intolerant does not mean you're allergic to dairy. It means you lack the enzyme (lactase) needed to break down lactose and usually results in gas or an upset stomach. However, butter is high in fat and low in lactose, so a lot of lactose intolerant people can eat butter or food containing butter just fine.
