We used to sing it this way at AIESEC meetings back in the ninetees:

This is number one and the fun has just begun...
This is number two and my hands are on her shoe...
...three and my hands are on her knee...
...four and the clothes are on the floor...
...five and the girl is still alive...
...six and she's crazy 'bout my tricks...
...seven and I think that I'm in heaven...
...eight and the girl cries I can't wait...
...nine and I take her from behind...
...ten and I use my fountain pen...
...eleven and she says let's start from seven...
...(any large number ending on "four") and she still cries for more