At the age of 12 Kaitlin needed to shave her hair off in order to have reconstructive surgery from a skull fracture after she was involved in a bicycle accident.
Kaitlin enjoys watching Curb Your Enthusiasm, The Office, Intervention and American Dad.
Kaitlin's favourite bands/artists are Johnny Cash, The Beatles, DJ Quik, Otis Redding, Ray LaMontagne, Cypress Hill, House of Pain, Hall and Oates, Pearl Jam and The Pharcyde.
Kaitlin's height is 5'8" (1.73 m).
Kaitlin attended the University of Oregon, she graduated in 1997 with a Bachelor's degree in Theatre.
Kaitlin is engaged to It's Always Sunny In Philadelphia co-star Rob McElhenny. They have been engaged since December 2007.
She had her first big break in a the 2005 TV series It's Always Sunny In Philadelphia as the character Deandra 'Sweet Dee' Reynolds. Before that, she was a guest star on a few shows and was on a reality show in 2002 called Meet The Marks as Kaitlin Marks.
Kaitlin: (On choosing the right roles) I wasn't in a hurry to take everything that came along. It's pretty important to me to be proud of the work I do. I didn't want to just be cute and on TV. I wanted to be funny.
Kaitlin: (On co-stars Glenn Howerton, Charlie Day and Rob McElhenney) They have a respect for each other that is amazing. They are able to argue and listen to each other without getting defensive ... and that makes it a really comfortable place to voice your own opinion and offer ideas.
Kaitlin: (On what drew her to comedy) I don't know. My dad's really funny... that's sort of how I coped growing up; I would just make fun of myself. I was really shy, and it kind of just turned into that, I think. It goes back to why I like the characters on our show; they're just so damaged, and there's something really funny about turning that around and making fun of it.
Kaitlin: (On being the only girl on It's Always Sunny In Philadelphia) I feel happy to be the only girl on the show. We get along really well, we're all really good friends now, I don't feel left out. I think that they were surprised that a girl could hang out and have fun with them, and I was like, "Really? You guys don't know any funny women? That's too bad.
Kaitlin: (On Myspace and being shy at school) I was really, really shy. It's funny, because we all have MySpace pages for the show, and I get contacted a lot now by people that I went to high school with, and every single one of them is like, "What? I can't believe that you're doing that! You were so quiet!" I think inside I just had a quiet plan to do it, but I certainly never shared that with anybody. I was scared of everything, so I didn't open my mouth very much.
Kaitlin: (On who she would like to work with in the future) I'm just a giant fan of Will Ferrell and Sasha Baron Cohen. They make me laugh so hard, I make hideous noises and that's a good sign. I also love Michael Cera; I think that kid is hilarious. And Annette Bening. She's one of my heroes. I think she's amazing because she's hysterically funny without trying too hard.
Kaitlin: (On preferring stage of television acting) Wow, that's a good question. I really love stage. When I moved here, I did the Groundlings and the Sunday Company and so we were performing every week, and it was a new sketch-comedy show every Sunday. And there's just something so fun and exciting about that, and it's just much more fast-paced and much more instant gratification because you have an audience right there. I really love that, and I miss it. But you make money in TV [laughs].
Kaitlin: (On what she does when not acting) In my downtime….I play with my dog. I go to the movies. I live right at the beach, so I spend a lot of time on walks on the beach. Just stuff like that…I cook! I'm totally into cooking. I'm trying to teach myself how to cook. I just got a juicer, so I've been juicing like crazy. You have to be careful with vegetable juice because it'll give you diarrhea.
Kaitlin: (On the fans in Philadelphia) We shoot in some pretty sketchy neighborhoods in Philadelphia because it just happens that some of the episodes we've done have been about buying drugs or whatever...and we had this guy walk up to us who didn't have very many clothes on and he was either half asleep or something was wrong with him because he came walking straight towards us and we all kind of tensed up like "Oh my God what's happening?" He walks right up to Rob McElhenney and shook his hand and said "I love your show man." We were like "Oh my God! We'll take it." Those are our fans!
Kaitlin: (On breaking her foot while shooting It's Always Sunny In Philadelphia) It is a very exciting story. I was running up my stairs and... that's it! I slipped on a stair and broke my foot. It was those damn hardwood floors. It wasn't my fault. It wasn't the wine that I was drinking [laughs].
Kaitlin: (On going to University) I loved it. I don't think I really had a choice, because my dad was a Duck, but I loved it. It's beautiful, and it's fun. I really enjoyed Rennie's a lot. I got my fake ID taken away at Rennie's.
Kaitlin: (On working with Danny DeVito) I wish I had some dirt on Danny DeVito, but he is honestly the nicest, sweetest man I've ever met in my life. I love him, I love being around him. He's become like a part of our family. His wife and kids are amazing. Like, he's the happiest man I've ever known. He doesn't really have much to be sad about.
Kaitlin: (On choosing the role of Deandra 'Sweet Dee' Reynolds in It's Always Sunny In Philadelphia) I really like her insecurity. She definitely is despicable, you can't really argue with that. I don't think she's hate-able because it all stems from her raging insecurity and they're so mean to her. I think there is just something really funny about that to me.