This happened. I was getting deepthroat (in my mind I called in "gagging" but never openly to her because to me that was the main event and to her it was a peripheral phenomena) performed upon me by a dear lady friend of years gone by. I pushed in suddenly and with great excitement and caused her to gag and fart simultaneously. She was embarrassed and apologized but I was over the Moon. I've to recreate this circumstance with little success.