For Rivero's first film appearance, he was cast in René Cardona's movie "The Invisible Assassin" (1965) where he wears a mask throughout the film. His breakthrough role came in the Western "El Mexicano" (1966; directed by René Cardona), making him a star overnight in his native Mexico. Kicking off a string of westerns for the young actor, this movie was followed with "Pistoleros de la frontera" (1967). He also found time to appear in a few wrestling films, teaming with the famed Santo in "Operación 67" (1967) and in "El Tesoro de Moctezuma" (1968; with Amadee Chabot).