John Ratzenberger was born in Bridgeport, Connecticut and he attended the Sacred Heart University where he earned a B.A. in English. While in college Ratzenberger and a friend started an improvisational troupe called Sal's Meat Market, which they took on the road to England after graduation. Ratzenberger remained in England for 10 years. While there he landed roles in a handful of major British-based film productions including A Bridge Too Far (1977), Superman (1978), Yanks (1979), Star Wars: Episode V - The Empire Strikes Back (1980), and Gandhi (1982).

In 1981, while on a return trip to the U.S., Ratzenberger auditioned for Cheers. As the story goes, both he and George Wendt auditioned for the part of Norm Peterson. When the creators decided to go with Wendt, Ratzenberger asked if they had a bar know-it-all in the cast, and then put his improv skills to work, breaking into a 10-minute monologue that would eventually lead the producers to create the role of Cliff Clavin -- a blathering postal worker who is a font of completely trivial knowledge, and Norm’s best friend.

Ratzenberger’s chattering mama’s boy became the most ubiquitous of all the show’s characters, with appearances on six different series -- Cheers, The Tortellis, St. Elsewhere, The Simpsons, Wings, and Frasier -- during and after the show’s 11-season run.

Ratzenberger co-wrote two plays for television while in England, and he also directed several Cheers episodes. He has made quite a career for himself as a voiceover actor, particularly for Pixar Studios. To date he is the only actor to have voiced characters in every major production made by the studio. Ratzenberger can also be seen on John Ratzenberger's Made in America on the Travel Channel.

He is divorced from the mother of his two children, Georgia Stiny.