A triple entendre while on ecstasy, where the eye balls in the forehead roll back, your body temperature goes up and down almost as if its rolling, and in some males the testicles get pulled up into the body cavity as if they just rolled off.
In the game of pool, the big balls are the stripes, as opposed to the solids, which are called small balls. One can imagine that the solid-colored balls look smaller than the stripes, although they are all identical except in appearance.
John knocked in the nine ballfirst, so he got the big balls. (The nine ball is striped)