Kaitlin Willow Olson (born August 18, 1975 in Portland, Oregon) is an American actress. She is best known for playing "Sweet Dee" Reynolds in the long-running television series It's Always Sunny in Philadelphia.
- Coyote Ugly (2000) as Bidding Customer
- Leap Year (2010) as Libby
- Escape from Planet Earth (2013) as 3-D Movie Girl
- The Heat (2013) as Tatiana
- Vacation (2015) as Arizona Cop
- Finding Dory (2016) as Destiny
- Curb Your Enthusiasm (2000-07, 20) as Becky (7 episodes)
- The Drew Carey Show (2002-04) as Traylor (12 episodes)
- Punk'd (2003) as Field Agent (2 episodes)
- The George Lopez Show (2004) as Janet (episode: "Home Sweet Homeschool")
- It's Always Sunny in Philadelphia (2005-present) as Deandra "Sweet Dee" Reynolds
- The Riches (2007) as Hartley Underwood (5 episodes)
- Family Guy (2011) as Brenda Quagmire (2 episodes)
- Unsupervised (2012) as Carol/Danielle (7 episodes)
- Brickleberry (2012) as Ethel (Season 1; 10 episodes)
- New Girl (2014-15) as Ashley (2 episodes)
- Bob's Burgers (2015-19) as Helen (2 episodes)
- The Simpsons (2016) as Quinn (episode: "The Girl Code")
- The Mick (2017-18) as Mackenzie "Mickey" Molng (37 episodes)
- Flipped (2020) as Cricket Melfi (11 episodes)
- Space Force (2020) as Edison Jaymes (episode: "Edison Jaymes")
- Hacks (2021-present) as DJ
- Welcome To Wrexham (2022) as Herself
- The Lad-ette: A common character type for her, most notably her roles as Dee and Mickey. Her character on Curb Your Enthusiasm had shades of this when she returned in Season 10.
- Romance on the Set: She and her Always Sunny co-star, Rob McElhenney, started dating in secret during Season 2 of the show before getting married in 2008. Similar to Charlie Day and Mary Elizabeth Ellis, this makes the vitriol between their characters even more amusing to watch.
- Slapstick Knows no Gender: A staple of her characters, who are often subjected to as much physical pain and humiliation as any of the men, if not more so.
- Statuesque Stunner: She stands at 5'9", and her husband (Rob McElhenney) has stated that she actually is taller than him when she's in heels.