During the 1970s, Muņiz produced and acted in a comedy series named Los Garcia (The Garcias). In Los Garcia, he participated alongside his real life son Rafo Muniz and Gladys Rodriguez, playing their father and husband respectively. Los Garcia became one of the most successful television shows in Puerto Rican television history. In that show, he popularized the phrase Sia Mi Vida! (a phrase widely used in Puerto Rico by people when they get mad, and which has no similar phrase in English, but loosely translated, it would mean Damned be my Life!)
For a brief moment during the late 1970s and early 1980s, Muņiz was the owner of a television channel, Channel 7, or Canal 7, in Puerto Rico. In 1988, he became one of the largest minority owners of Teleonce, channel 11.
In 1990, he and Rodriguez reunited to act in the movie Lo Que Le Paso A Santiago, which was nominated for the Oscar as best foreign film. Hollywood critics have praised his acting and that of Rodriguez, saying that their acting was part of the formula that led the movie to be nominated. Muņiz played Santiago in that movie.
Another of Muņiz's kids, Pedro Muņiz, is also a well known actor and producer.