The locations of the men's and women's restrooms varies throughout the series. Usually the women's restroom is closest to the bar and the men's is closest to the pool room, however this is inexplicably switched on numerous occasions throughout the series.
The main entry door to the bar is always seen opening inward. Fire Codes mandate that any such entry/exit door open outward.
Cheers violates several fire code regulations. The main door opens inward, there are no illuminated "exit" signs, there is no emergency lighting, and the pool room should have a emergency fire exit.
In one episode, Frasier Crane states his father has passed away, but throughout the spin-off, 'Frasier', his father is well alive. However, in an episode of that series, Frasier explains to Sam that he made up his father's passing (and occupation) all along, due to a fight he had with him.
The year below the 'Cheers' sign reads "Est. 1895", even though the paintings in the opening (showing the bar's past history) could be older than that. However, in a later episode, Sam states the year was made up.
The "Bar Wars" episodes with Cheers against Gary's Old Towne Tavern are in Roman numerical order from Season 6 to Season 11. However, Season 8 contains the episode, "Bar Wars III" and then the next "Bar Wars" episode is listed in Season 10, but it's incorrectly named "Bar Wars V." There is/was no "Bar Wars IV."
In #10.23, John Kerry, appears briefly, as himself. In the credits he is listed as "Senator John Kerrey".
Apparently Cheers only serves generic beer and other alcoholic drinks. Unlike most bars, Cheers has no lighted signs, no beer taps showing different brands, and people order whiskey, gin etc. and no brand names are sought from customers.
In several of the later episodes of Season 2, the camera pans out from the corner of the bar (where Norm sits) and you can see a Theatre curtain on the left.
Early in the series, Frasier has a dog called Pavlov that he has great affection for. Later in the series, Frasier tells everyone that he's never liked dogs and can't stand been near them.