Cliff Clavin is a United States postal worker and a regular at the Boston watering hole called Cheers. An insufferable know-it-all, Clavin will say just about anything to get a rise out of his fellow bar patrons. Cliff is rarely successful with women, lives with his mother and once appeared on "Jeopardy!"
John Ratzenberger played Cliff from 1982-1993.—XFINITY Entertainment Staff (Photo: AP)
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