At 9:02, two men arise from their table and can be seen walking through Cheers towards the exit. Sam enters the bar, and at 9:27 the two men once again arise from their table, after already having exited the bar.
Frasier cliff and Norm talking about a pizza place near the airport cliff says the airport is about 1hr away from the bar it's actually only about 3.3 mi away from the real Cheers or about 12min.
When Carla says "Let there be dark!", and switches the bar light off, the lights go down before she hits the switch.