There is an extra at the bar who keeps breaking character. She's a red headed lady dressed in pink, who can't stop staring at the main actors and action taking place during the first ten minutes of the show.
"Wait 'till The Sun Shines, Nellie" was first published and recorded in 1905, 16 years after Cheers's 1889 opening.
The newspaper that Rebecca brings in gives Cheers' address as 112½ Beacon Street in Boston. Every exterior establishing shot of Cheers has shown it to be located at 84 Beacon Street a fifth of a mile away.