nightstallion

Can refer to two totally-different bed-related things:
(1) A good, happy, peaceful dream
(2) An exceptionally virile and energetic dude who literally wants to "do it till dawn".

I never understood why bad dreams were called nightMARES and good dreams are nightSTALLIONS... in the stock-breeding world, we all know that mares are much easier to saddle-break than stallions, so why give "da ladies" such a bad rap??