Every bar has its annoying know-it-all, a guy who blathers on at length about everything and anything, little of it being relevant to the conversations at hand or of interest to anyone within earshot. At Cheers, postal worker Cliff Clavin is that guy. A natural-born rambler, Cliff is a veritable font of knowledge more trivial than useful. The only person who really seems to pay him any mind is his best buddy, Norm Peterson. The two sit elbow-to-elbow each night, enjoying their after work beers, neither too eager to head home.

Unmarried mama’s boy Cliff still shares an apartment with Ma Clavin (as she is called), who treats her middle-aged son like he’s still a child. The two are inextricably co-dependent (Pa Clavin cut out when Cliff was still a boy). It's virtually impossible for Cliff to have anything vaguely resembling a love life. So he lives vicariously through Sam and his sexual intrigues. Cheers is a sanctuary for Cliff, where he can escape his mother’s nagging and find a little breathing room. So what if he’s perpetually being ridiculed by Carla? He’ll take it over hovering Ma Clavin any day.

There’s a bit of the tragic clown in Cliff. Though he loves his job at the post office, he does have dreams of bigger things. He gives stand up comedy a try and even pens a few jokes for The Tonight Show, but Cliff’s proudest moment is also his saddest -- a doomed appearance on Jeopardy.

When Cliff’s mother sells their family home and moves to Florida on the profits, he’s both elated and terrified at being without her. That fear is quickly alleviated when he moves into an apartment and begins dating a neighbor. It’s his first relationship -- ever! The love of Cliff’s life is fellow postal worker Margaret O'Keefe, an equally enthusiastic postal employee Cliff meets when she is assigned to train with him. All goes well for the two, until the night of a secret tryst involving the use of a postal vehicle, for which Margaret is reprimanded. Humiliated and disappointed in herself, she flees to Canada, leaving Cliff heartbroken. When she returns she demands a commitment from Cliff, which causes him to suffer a temporary case of hysterical blindness.