John Dezso Ratzenberger is an American actor. He is best known for playing the character Cliff Clavin on the comedy series Cheers, for which he earned two Primetime Emmy nominations. Ratzenberger also played a role in the short-lived spin-off The Tortellis and in an episode of Wings, which was made by the same creators. He has voiced various characters in several Pixar animated feature films including Hamm in the Toy Story franchise, The Abominable Snowman in the Monsters, Inc. franchise, Mack in the Cars franchise, The Underminer in The Incredibles franchise, Fritz in the Inside Out franchise, and many others.

Clifford C. Clavin, Jr. is a fictional character on the American television show Cheers played by John Ratzenberger. A postal worker, he is the bar's know-it-all and was a contestant on the game show Jeopardy! Cliff was not originally scripted in the series' pilot episode, "Give Me a Ring Sometime", but the producers decided to add a know-it-all character and Ratzenberger helped flesh it out. The actor made guest appearances as Cliff on The Tortellis, St. Elsewhere, Wings, and Frasier.