(at around 24 mins) Someone from the back room yells to Carla about the beer they ordered from her. Carla was there on her day off, and no one ordered anything from her.
(at around 6 mins) While talking to Carla, Big Eddie states that since 1918 the Yankees have won 23 World Championships. The Yankees had only won 22 World Championships throughout the entire run of Cheers. They won their 23rd in 1996.
(at around 23 mins) A patron stands up and in a thick Boston accent says he's a Boston Bruin, but only four Americans were on the 1982 team, and none were from Boston.
(at around 12 mins) When Sam is telling Carla that he may have to fire her, he gets up and walks towards the bar. The overhead boom mike is visible right in front of the bar TV in the upper right-hand corner of the frame.