Kaitlin Olson, American actress was a cast on a television show called It's Always Sunny in Philadelphia in 2005.
It 's Always Sunny in Philadelphia is an American television black comedy sitcom that premiered on FX on August 4 , 2005 . Kaitlin Olson . She began her career in the Groundlings , an improvisational group in Los Angeles , California , and had minor roles in several television series before being cast as Deandra `` Sweet Dee '' Reynolds on the FX black comedy series It 's Always Sunny in Philadelphia in 2005 .