Why did Marcello Mastroianni become Federico Fellini’s cinematic alter ego?

Marcello Mastroianni became Federico Fellini’s cinematic alter ego because he possessed a versatile screen presence that allowed him to embody the director’s personal visions and experiences. Their collaboration began with La dolce vita (1960), where Mastroianni’s performance helped define the film's exploration of modern life.12

The relationship deepened significantly in the Academy Award-winning film 8 1/2 (1963). In this work, Mastroianni portrayed a famous film director who was explicitly based on Fellini himself, struggling with creative paralysis and personal dilemmas. By casting Mastroianni as his surrogate, Fellini was able to project his own internal conflicts, dreams, and fantasies onto the screen, effectively using the actor as a vessel for his most personal narratives. This partnership continued through various projects, including the abandoned The Journey of G. Mastorna, further cementing Mastroianni's role as the primary interpreter of Fellini’s unique, often surreal, cinematic world.12