Charlie Day may play the nerdy scientist in Pacific Rim, but don’t let the sheepish facade fool you. He’s kicking alien butt and taking names in the big budget apocalyptic sci-fi flick -and he’s even ready to demonstrate his movie-trained skills off camera should the end of the world come sooner rather than later.

“I’m fighting back with the rest of the human race! This guy’s not going down,” Day told Celebuzz at the Hollywood premiere July 9. “I’m going to pull tails of Kaijus, I’m going to kick them in their lizard balls, I’m going to do whatever I can do… I’m gonna scratch their eyes… I’m going down swinging!”

But he’s realistic about how things on Earth could really end if it came down to the Kaiju or the human race – breaking wind: “I think Mother Nature will just fart us off the planet.”

The funnyman plays the manic Dr. Newton Geiszler in director Guillermo del Toro‘s highly-anticipated action thriller where the human-piloted Jaeger robots come to epic blows with the Kaiju monsters that are intent on destroying the world.

But forget massive mechanical robots throwing punches, the It’s Always Sunny In Philadelphia star is just happy to play the smart guy (for once).

“This guy can read and write!” he added. “That’s refreshing. It’s fun to play a guy who’s cocky and arrogant and the smartest guy in the room.”

For more with Charlie Day, check out the CB! video above.

Pacific Rim hits theaters July 12.