"Joker" is no laughing matter.

First reactions to the highly-anticipated film, which hits theaters October 4, are coming in on social media after its screening at the Venice International Film Festival Saturday.

And the buzz for the Joaquin Phoenix-led film is mostly positive. Here are some of the most noteworthy reactions so far:

"JOKER is one of the true masterpieces of the superhero cinema, and one of 2019's greatest achievements," Forbes contributor Mark Hughes shared on Twitter.

ScreenDaily's Tim Grierson said, "Folks, JOKER is great."

Geeks of Color founder and editor-in-chief Dorian Parks gave Phoenix major praise.

"Joaquin Phoenix's performance in #JokerMovie is nothing short of Oscar-worthy. He fully commits to the role mentally and physically," he tweeted. "Todd Phillips delivered a game-changing comic book film, and I cannot wait to see it again."

IGN's Jim Vejvodasaid, "Joker isn’t just an awesome comic book movie, it’s an awesome movie, period."

CinemaBlend's Eric Eisenberg alluded to the film being complex.

"You’ll definitely feel like you’ll need a shower after seeing it, but once you’ve dried off and changed clothes, you’ll want to do nothing else but parse and dissect it," he wrote.

Others weren't entirely convinced.

Vanity Fair's Richard Lawson said, "JOKER is going to be, and should be, very controversial."

Why so serious, Oscar?:5 reasons why Joaquin Phoenix's 'Joker' is a bona fide awards threat

From 'It 2' to 'Joker':10 movies you absolutely, positively must see this fall