Personally, I'm a fan of jumping rope (it's easy enough for a five-year-old girl yet hardcore enough for heavyweight boxers), and I just found this short TV commercial on the CN Upfront site:
http://www.cartoonnetwork.com/promos/upfront/
You have to navigate through "Get Animated" first and then click on "Jump Rope". It features the Foster's main imaginary characters and real-life schoolchildren playing double-dutch (Bloo is singing rhymes, Coco lays an egg, Ed is being Ed, and Wilt getting tangled, since he's so tall).
Sorry if this is old or mentioned here already, I did a superficial search and didn't find anything related.