EMERYVILLE, CA.

Long before he became the lovable shnook, Charlie Kelly on FX's cult sitcom, It's Always Sunny in Philadelphia, Charlie Day went to Merrimack College hoping to one day play professional baseball.

That didn't work out and he turned his attention to theatre, performing mainly dramatic roles in regional productions.

This summer he swings to both ends of the spectrum -- broad comedy in Pixar's Monsters University and life-or-death drama in the giant monster epic, Pacific Rim.

"It wasn't until Rob McElhenney, Glenn Howerton and I decided to make It's Always Sunny in Philadelphia that I started doing comedy," Day tells reporters on the campus of Pixar Animation, adding, "I didn't set out to be a comedic actor."

The show's cult following includes Robin Williams, Sean Penn, Samuel L. Jackson and evidently some of the artists at Pixar who called him in for their latest, Monsters University. Day plays Art, a fuzzy purple arc-shaped character with a loose grip on what the heck is going on. His roommates are Mike and Sulley, younger versions of the Cyclops and his blue beast best friend from 2001's Monsters Inc. In this prequel, the pair competes to enrol in the school's prestigious Scare Program.

Day didn't even have to audition for the part. Instead, the Pixar people surprised him with a rendering of his character animated to lines from It's Always Sunny.

"I'm not even sure he's a student at the college, he's maybe crashing there," Day says about Art. "Nobody knows his story. I assume he's some sort of a marsupial but I can't tell. We just know that he's a very happy-go-lucky guy. He's an optimist but he's got a mysterious past and I guess he's been incarcerated."

Art is another goofy role in a string of hapless characters ranging from Justin Long's best friend in Going the Distance, to Dale Arbus in Horrible Bosses, a dental assistant and the enviable object of Jennifer Aniston's sexual advances.

But his next movie is a bit of a turn to the serious side, Guillermo del Toro's upcoming $190 million, Pacific Rim.

"One monster you want to pet, the other one is going to eat you," he jokes about transitioning from Monsters University.

"I play Dr. Newton Geiszler. It was wonderful to be given a character who can actually read. It was fun to get to do something that wasn't just pure comedy."

Geiszler is an expert on the kaiju, monsters that rise up from the ocean floor to decimate earth's cities.

"I definitely have a joke or two," explains Day. "It's not too unlike Jeff Goldblum in Jurassic Park. He'll make you laugh occasionally but you also do worry about whether or not he's going to be eaten."

When asked if he does indeed get eaten, Day changed the subject.

Things are going well these days and he doesn't want to jinx it. Married to actor Mary Elizabeth Ellis, who has a recurring role as the waitress on Sunny, when Day isn't working he's busy with his baby boy, Russell Wallace.

Day's career to date has leaned more R than G, which is one of the reasons he made Monsters University.

"I do think it will be nice to have a movie that my son can watch pretty soon," he says, adding with a smile, "Although if he wants to watch Sunny I wouldn't really have a problem with it."