I don't know about you, but I haven't run into many examples of NSFW-ish fan art devoted to Nintendo's pugilistic Punch-Out!! series over the years--which, in my humble opinion, is a crying shame.
Sadly, the piece of saucy fan art below (titled "Sweet Dream") doesn't include Little Mac, but it's so appealing even without his presence that I won't spend too much time complaining about the oversight.
This drawing was produced by the hand of artist Pauli Kohberger (aka madamluna), by the way. To see more of her stuff, check out her deviantart gallery (which contains a number of additional Punch-Out!!-inspired pieces) or her site, Electric Stories.
See also: 'Kirby and Meta Knight en fleur'