Originally posted by: dballin
It's not 96%, but 96 exits. I'm pretty sure Bowser counts as an exit, so it might only show 95. I'm not sure actually. Been a while.
World 5 would be Forest of Illusion
Yep, 96 exits. Nope, Front Door and Back Door do not count towards your exit count, neither does Yoshi's House, Top Secret Area, or any other levels that "end" by touching the sides of the screen (except any level that ends with Yoshi's Wings).
As others have said, common places people miss exits are Star World, any ghost houses and Forest of Illusion. Don't forget Chocolate Secret 4 (I think), the level where you can end up going in a circle on the overworld.
Basically, any red level dots must be cleared twice using both exits.