Here's the link about the superman thing...
http://www.rawbw.com/~svw/superman.html
here's a little bit of what it says...
"Lastly, he'd blow off the top of her head.
Ejaculation of semen is entirely involuntary in the human male, and in all other forms of terrestrial life. It would be unreasonable to assume otherwise for a kryptonian. But with kryptonian muscles behind it, Kal-El's semen would emerge with the muzzle velocity of a machine gun bullet. (*One can imagine that the Kent home in Smallville was riddled with holes during Superboy's puberty. And why did Lana Lang never notice that?*)
In view of the foregoing, normal sex is impossible between LL and Superman.
Artificial insemination may give us better results. "