Kaitlin Willow Olson (born August 18, 1975 in Portland, Oregon) is an American actress. She is best known for playing Deandra "Sweet Dee" Reynolds in the 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, 2020) 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 (2014-2015) as Ashley (2 episodes)
- Bob's Burgers (2015-2019) as Helen (2 episodes)
- The Simpsons (2016) as Quinn (episode: "The Girl Code")
- The Mick (2017-2018) as Mackenzie "Mickey" Molng (37 episodes)
- Flipped (2020) as Cricket Melfi (11 episodes)
- Space Force (2020) as Edison Jaymes (episode: "Edison Jaymes")
- Hacks (2021) as DJ
- 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.