Other mistake: Mike asked Carol where his checkbook was because he needed it to buy her a Christmas present. Carol pulled open the kitchen drawer she was conveniently standing next to, got the checkbook out, and handed it to Mike. A little later when Carol is telling Peter about her secret plan, she points out that she will be using their (Carol and Mike's) "special savings account." There would be a separate book for making deposits/withdrawals from the savings account, so it doesn't make sense for Mike to be using regular checking account to buy the present. (00:03:06 - 00:05:34)
Suggested correction: Except, Mike wouldn't just draw out money and take cash to the travel agency. He likely transferred the money to checking and therefore would still need a check to write out to the travel agency.
Other mistake: Watch when Carol is singing "Oh Come All Ye Faithful," as she walks down the line of on-lookers, an extra in the back moves along with her and keeps looking at the camera.
Character mistake: Cindy tells Greg she hasn't worn curls for 12 years. This is incorrect because in the original series, she changed from curls to braids by 1973 and then to straight hair by 1974. This story takes place in 1988 so technically, she hasn't worn curls in around 15 years (not 12).
