Kaitlin Willow Olson McElhenney (born August 18, 1975) is an American actress, comedian, and producer. She began her career in The Sunday Company at the Groundlings, an improvisational theatre and school in Los Angeles, California. She had minor roles in several television series before being cast as Deandra "Sweet Dee" Reynolds on the long-running FX comedy series It's Always Sunny in Philadelphia (2005–present). Olson starred as Mackenzie "Micky" Murphy in the Fox comedy series The Mick (2017–2018) and as Cricket Melfi in the Quibi comedy series Flipped (2020), which earned her a nomination for the Primetime Emmy Award for Outstanding Actress in a Short Form Comedy or Drama Series. She has also appeared in films including Leap Year (2010), The Heat (2013), Vacation (2015), Finding Dory (2016), and Arizona (2018). She has been married to actor Rob McElhenney, her co-star on It's Always Sunny in Philadelphia, since 2008.

Filmography

• High Potential — Morgan Gillory, Producer, Executive Producer
• 2024Incoming — Ms. Nielsen
• Agent Elvis — CeCe Ryder (voice)
• 2023Champions — Alex
• 2022It's a Wonderful Binge — Mayor Spengler
• Abbott Elementary — Dee
• Hacks — DJ Vance
• Flipped — Cricket Melfi
• Space Force — Edison Jaymes
• 2018Arizona — Vicki
• The Mick — Mackenzie 'Micky' Murphy
• 2016Finding Dory — Destiny (voice)
• 2016Marine Life Interviews — Destiny (voice)
• 2015Vacation — Arizona Cop
• 2013Escape from Planet Earth — 3D Movie Girl (voice)
• 2013The Heat — Tatiana
• Brickleberry — Ethel Anderson (voice)
• Unsupervised — Carol / Danielle (voice), Carol (voice)
• Bob's Burgers — Helen (voice)
• New Girl — Ashley
• 2010Held Up — Rocky 2
• 2010Leap Year — Libby
• 2009A Very Sunny Christmas — Deandra "Sweet Dee" Reynolds
• 2009The Nightman Cometh: Live — Dee Reynolds
• 2009Weather Girl — Sherry
• The Riches
• It's Always Sunny in Philadelphia — Dee Reynolds
• Kelsey Grammer Presents: The Sketch Show
• Out of Practice
• Miss Match — Jillian
• Punk'd — Field Agent
• George Lopez — Janet
• Meet the Marks
• 2000Coyote Ugly — Bidding Customer
• Curb Your Enthusiasm — Cheryl's Sister, Becky
• 2000Eyes to Heaven
• Family Guy — Brenda Quagmire (voice)
• The Drew Carey Show — Traylor
• The Simpsons — Quinn Hopper (voice)

Appearances as themselves (9)

• 2025PaleyLive: It’s Always Sunny in Philadelphia 20th Anniversary Celebration! — Self
• Welcome to Wrexham — Self
• Who Wants to Be a Millionaire — Self - Contestant
• The F Word — Self
• Late Night with Seth Meyers — Self, Self - Guest
• 2011A Tribute to Ryan Dunn — Self
• Conan — Self
• Jimmy Kimmel Live! — Self - Guest
• The View — Self