Corrected entry: Sam's friend Eddie shows up and says they made a bet a year ago while drinking tequila. This isn't possible, prior to his "falling off the wagon" when Diane left he hadn't had a drink in about five years (he told Diane 3 years in the pilot episode) and a year hadn't passed since he's fallen off the wagon when Diane left.
Rebound (2) - S3-E2
Corrected entry: When Carla asks Frasier if he's "taken a good look at everyone else", the camera pans to the bar patrons. Dianne is sitting at the bar smiling. She wouldn't be drinking at Cheers because of her recent falling out with Sam. Dianne then comes in the bar looking for Frasier a minute later wearing different clothing. (00:06:50)
Correction: Just watched the scene and while the person has a slight resemblance to Diane, this is a different actor.
Correction: I am a recovering alcoholic, and teetotal, but even I occasionally have a relapse, generally when meeting old drinking buddies. I regret it to hell the next morning, but it happens - to me and to Sam.