Charlie Day is an American television and film actor and writer best known for playing Charlie Kelly on the television series It's Always Sunny in Philadelphia. He portrays Newton Geiszler in Guillermo del Toro's Pacific Rim.
Aside from his work on It's Always Sunny in Philadelphia, Day is also the series executive producer and one of its writers. He has appeared on several other television shows such as Third Watch, Law & Order, and Reno 911!.
In 2010 he starred film Going the Distance, alongside Drew Barrymore. In 2013, he voiced a character named Art in the Pixar animated film Monsters University. He co-starred in New Line Cinema's Horrible Bosses in July 2011, opposite Jason Bateman, Kevin Spacey, Jennifer Aniston and Jamie Foxx.