It might be possible that this is the best sentence I've read in a long time:
Lastly, Bering explains how a woman can get pregnant by a man she never had sex with:
If "Josh" were to have sex with "Kate" who recently had sex with "Mike," in the process of thrusting his penis back and forth in her vagina, some of Mike's semen would be forced under Josh's frenulum… Were Josh to then have sex with "Amy" several hours later, it is possible that some of the displaced semen from Mike would still be present under his foreskin and thus may be unwittingly transmitted to Amy who, in turn, could then be impregnated by Mike's sperm. Of course, all of these people would need to be obsessed with dick".
I might try this one day, just because I can.
It was taken from a report on 'Scientific American', obviously I wasn't reading that, it was brought to my attention by Jezebel, like all the good stories I write about. If you'd like to read the whole article click here.