Charlie Day is best known so far for his work on "It's Always Sunny In Philadelphia," and that's as it should be. After all, he's a major creative partner in the production of the show, and it fully expresses a totally lunatic sensibility that Day seems very proud of, each and every week.

This summer, though, Day shows up in a few very different films. There is, of course, Guillermo Del Toro's "Pacific Rim," where Day plays a scientist who is the leading expert on the kaiju, the giant monsters that threaten our planet. I'll be publishing some looks at my time on the set next week, and a lot of what we watched involved Day, Ron Perlman, and something that was not there. Watching him work for a full day in that sort of environment, I was really impressed by how much Day threw himself into every take, into even the angles where he wasn't the focus of the shot. He seemed to be able to summon it up every time, and knowing Del Toro… knowing what he asks of his actors… I could tell that he felt like he had found another missing piece from his always-growing movie family.

In "Monsters University," Day voices one of the members of Oozma Kappa, the fraternity that is joined by both Mike (Billy Crystal) and Sully (John Goodman) in order to enter the Scare Games. It's a competition that basically just gives one of the frats bragging rights for a year, but in the film, the stakes are escalated because the future of both Mike and Sully at the school hangs on whether or not they can win these events with this team of misfits. Art, Day's character, is a good example of a monster that isn't particularly scary because he's just too darn nice.

Day doesn't seem terribly precious about what he does as an actor, and I like that about him. He's pretty blunt about what is required to do a voice for a film like this and how a lot of it isn't about character at all, but is more just Foley work to fill out the big long action scenes.

I'm sure I'll be talking to him again about "Pacific Rim" very soon. Until then, here's Day on his first film for the summer of 2013.

"Monsters University" opens June 21st, 2013.
"Pacific Rim" opens July 12, 2013.