I think he said "waterslide" becuase 1) it sounds funny and 2) because of the water parks. As for what made him mad at Disney, first there was the whole thing about Aladdin about 10 years or so ago that was fairly drawn out, then things were "mended" and now after all of Robin's films with Disney (Flubber, Bicentenial Man) were poorly marketed and did not do exceedingly well at the box office, I think he's a little bitter again.