When she was just 13, Addison spearheaded a reunion production of the Broadway hit Annie for the benefit of the Cystic Fibrosis Foundation and Children's Hospital of Philadelphia (CHOP), where her cousin's life was once saved. She also has a family friend who is afflicted with Cystic Fibrosis.
In May 2003, Timlin made her Broadway debut performing the role of Baby Louise in the revival musical Gypsy at Shubert Theatre. The production ran until May 2004. She also played July in the 2002 Paper Mill Production of Annie. She also portrayed the role of Mary Lennox in The Secret Garden.
In 2006, Addison played Maddy in The Isabel Fish. She also portrayed the role of Amy in Afterschool (2009) and was in the 2008 film Man.
She was in the "Sleeping Lessons" music video by The Shins and appeared as Juliet in We the Kings' video for "Check Yes Juliet".
Her mom Jayne Timlin, an assistant at a mortgage firm, is divorced from her father, R.J. Timlin, who is a real estate agent in Bucks County, Pennsylvania. She has two older sisters, Keely and Breana, and a brother.
Addison is 5' 1" (1.55 m) tall.
Addison: I really believe that Lindsay Lohan, who I think is a really good actress, is in the position she is in because she is an idol to teenage girls. It's just too much pressure.
Addison: You do grow up fast in the business. When I left school to do Annie, I was 9, and I came back like, 35. You spend a lot of time with adults.
Addison: (on acting) I feel like a lot of my friends who work now don't want to do it when they're older. Some of them are, like, 'This is fun now, but when I grow up I want to be a mom in New Jersey.' And I'm, like, 'That's weird.' For me, I know this is what I want to do. I've always felt like this is what I've wanted to do. Forever.
Addison: (about working on "Day One") The cast have started to create this little family after the first week, you know. We've been through some stuff now. And everyone's getting along really well. It's just been such a dream.
Addison: (about loving her character on "Day One") What I love about her, she's pretty tough and she has like these two guys that are helping her out and saving her life. But at the same time, you can't see her grabbing for them. And her helping them out. Pulling herself on her own. And I like that she's getting the hang of this.
Addison: (on doing the film "Afterschool") I'm so excited to be here at the Miami Film Festival. I got to go to the Cannes Film Festival and New York Film Festival. And both of them were such wonderful experiences, but here, especially the weather has really been a nice change from New York. But everyone is just so nice and it's really great to see these films and being in an American Film Festival and to be able to represent Afterschool. It's something I'm very proud of and I'm very happy to be here. It's been a really great time.
Addison: (describing sleepovers with her friends) Every time Feeni sleeps over my house, we make this instant Thai food, and we eat that with chocolate milk. And then we make the comfiest bed, and then we just talk, like, about our future. And it's like, 'Oh, my God, our future.'
Addison: I don't want to be a teeny-bopper type of actress. I don't want to do kids' movies, like Spy Kids and Sleepover and Confessions of a Teenage Drama Queen. I would kill myself.
Addison: (on when she asked her parents to accompany to Manhattan for an audition) They were like, 'Oh, we'll go to New York, we'll go shopping, we'll go see The Rockettes, and also you can do your audition,' But I was very serious about it. I was three feet tall, and I was, like, focused.