I remember being able to put a 1x1 round brick into the top of a minifig cup before my dark age (the period of time that a person stops building with Lego, up to the time they pick up the bricks again), but I have tried it since and can't do it.
Was I imagining that connection, or have they redesigned the minifigure cup?
Is/was there another connection that I might have confused with the minifig cup?
(This would have been sometime in the 80's, but the bricks in my collection went back to the '70s.)