Kaitlin Olson was a part of the improvisational group The Groupies .
Kaitlin Olson began her career in The Groupies , an improvisational group in Los Angeles , California , and had minor roles in many television series before being cast as Deandra `` Sweet Dee '' Reynolds on the FX black comedy series It 's Always Sunny in Philadelphia in 2005 .
Kaitlin Olson