The first time I had anal sex, I was having vaginal intercourse and she was facing me, while sitting on my lap. She was pretty much controlling the tempo for the most part. After a while she began bouncing up and down. The next thing I know, my penis is up her ass and she does not miss a beat. She kept bouncing up and down until we both came. Afterwards she asked me if I came up her ass, I told her I did. There must have been enough lubrication around to make that an easy transition. It do not think it was her intention to end up with my dick up her ass, but we both enjoyed the end result.