David Lynch's Mulholland Drive ending has to be one of the most confusing conclusions I've ever seen. The blue box, the old couple shrinking, the cowboy saying "time to wake up" - I've watched it three times and I'm still not sure I understand the Mulholland Drive ending. Is it all a dream? A dying fantasy? Multiple realities? I'd love to hear some coherent theories about the Mulholland Drive ending because my brain hurts trying to figure it out.
Mulholland Drive ending is about the collapse of fantasy into reality. The first two-thirds are Diane's idealized version of her life and relationship with Camilla. The Mulholland Drive ending reveals the truth - she's a failed actress who hired a hitman to kill her successful ex-lover, then kills herself out of guilt. The blue box contains the truth she can't face.
I think the Mulholland Drive ending is more about the nature of Hollywood dreams and nightmares. The fantasy sequences represent the glamorous version of Hollywood, while the Mulholland Drive ending shows the brutal reality. It's about how the movie industry sells dreams while crushing people. The Mulholland Drive ending exposes the darkness behind the glitter.
From a film theory perspective, the Mulholland Drive ending deconstructs narrative itself. Lynch is playing with our expectations of how stories should work. The Mulholland Drive ending isn't meant to be solved like a puzzle but experienced as an emotional journey through desire, guilt, and self-deception. The ambiguity is the point.