Favreau began his television career as a regular on La Boîte à surprise, a long running children's television show on Radio-Canada. At that time, he was teamed with another clown in an act called Bim et Sol. Favreau developed Sol's monologues into an enormously popular one-man show. Favreau then teamed up with another clown for Sol et Bouton. Finally, Favreau created, with Luc Durand a popular television series called Sol et Gobelet.
Later, he played numerous roles on stage and on several television series on Canadian television, such as Parlez-moi, an instructional program on the French language on TVOntario in the late 1970s. Many English Canadian children got their first exposure to Quebec French through Favreau's work. He is best remembered for the witty deconstructions of the French language which he invented for Sol.