Warner Bros.

What's so funny? Certainly not this "Joker."

The first teaser trailer for the Batman villain's origin story is here, and man, it's dark. It's brooding. It's basically "Taxi Driver," but with a comic book character as Travis Bickle.

Joaquin Phoenix stars a troubled man named Arthur Fleck who is beaten down, made fun of, and constantly harassed until he begins to descend into madness. The clown make-up he wears for his job starts to become a mask he needs to survive.

The teaser definitely gives off the vibe of a gritty character study, which is what director Todd Phillips ("The Hangover") intended.

As cast member Marc Maron recently said, “The approach that Todd Phillips has taken is more of an origin story and a character study of a mentally ill person that becomes The Joker. It’s more of an intimate and gritty movie with a very specific scope. It’s going to be really interesting to see how it comes out.”

And the homage to "Taxi Driver" is even clearer since Robert De Niro also stars in this movie.

"Joker" opens in theaters October 4.