Guybet began acting in French film and TV with mostly small parts beginning in the mid 1960s. His first major role was a supporting turn in 1973's The Mad Adventures of "Rabbi" Jacob, as chauffeur Salomon. More comedies followed, including The Return of the Tall Blond Man with One Black Shoe with Jean Rochefort (as one of the assassins) and co-starring parts in the WWII French army comedies On a retrouvé la 7ème compagnie! (with Pierre Tornade), La 7ème compagnie au clair de lune, and Général... nous voilà!. 1978 saw his only starring role, in Le pion (or The Pawn).
By the 1990s, while continuing to play character roles, Guybet entered dubbing, lending his voice to Dilat Laraht on the French animated series Iznogoud, Stimpy on Ren and Stimpy, and Mr. Tweedy in Chicken Run. For Pixar dubs, he voiced Rex in the Toy Story franchise, Molt in A Bug's Life, and Yeti in Monsters Inc.