I voted EPCOT as I love the WORLD SHOWCASES!!! How awesome that would be to spend as much time as I want in each showcase sampling cuisine from each one!!
I would love being "trapped" in the Magic Kingdom.. Animal Kingdom is a close second for me as well..
Being a Fitness Fanatic, I also thought about the classes I would love to teach (I'm a fitness instructor) in each park: I would love to do some Yoga in front of the Tree of Life in AK... As well as Tai Chi(which is inspired by animals). I would have loved to do a hard rocking old fashioned Hi/Lo cardio class in front Rock and Roll Coaster at MGM-the energy is so High there. The music rocks!!! I would have done Kickboxing at the Japanese Pavilion at Epcot- as well as Karate-which has it's origins there. Plus that really cool statue of the Samuria's are awesome!! Plus I would have love to jog Around the World! I think doing some aqua classes in the Typhon Lagoon against the waves would have been a Blast!!
I would have loved to teach a step class right by the bridge of Splash mountain-that way when hot just get on bridge/ride and get cooled down fast! The idea of doing walking lunges and squats down Main Street totally appealed to me as well.
*Of course, I would love Mickey, Minnie, Goofy and the whole crew to join..
Perhaps Mickey needs a Personal Fitness Instructor- After all he's 75..
While I love Magic Kingdom, if I were to be trapped I would choose MGM and do WWTBAM (it's addicting) all day, lunch at Brown Derby and finish up at Fantasmic!