Hibari Kyouya travels in time and takes over the world. Basically crack.

Itachi was a good looking troubled teenager left to wander the country unsupervised in the company of a group of insane criminals. He may have made a few questionable decisions involving alcohol and women. It is also worth noting that no-one actually got around to explaining the use of a condom to him. The results are depressingly predictable. Or the one where Itachi missed shinobi sex ed and ended up creating spawn across half the elemental nations, which Sasuke somehow ends up responsible for.