http://www.redboots.net/comics/moswok.htm<snip>
Assume a mating between Superman and a human woman designated LL for convenience.
Either Superman has gone completely schizo and believes himself to be Clark Kent; or he knows what he's doing, but no longer gives a damn. Thirty-one years is a long time. For Superman it has been even longer. He has X-ray vision; he knows just what he's missing.2
The problem is this. Electroencephalograms taken of men and women during sexual intercourse show that orgasm resembles "a kind of pleasurable epileptic attack." One loses control over one's muscles.
Superman has been known to leave his fingerprints in steel and in hardened concrete, accidentally. What would he do to the woman in his arms during what amounts to an epileptic fit?
<snip>
Read the whole thing at the link, it's really both hilarious and kind of sad at the same time.