I fell asleep through one of the early Harry Potter films, my Daughters pestered us to take them at the time, I had just finished night duty and was tired anyway, and could not remember anything about it afterwards!
The second time was when I went to a boring after Dinner history lecture by a retired Admiral, my husband's idea, not mine! It was onboard a Cruise ship, and was partly down to his droning voice, and partly the fact that I wasn't in the slightest bit interested in what the pirates and battleships did many years ago!
I could hear rumbles of snoring coming from the rows of seats behind me, and before l knew it, I had joined them, waking up only as the bright lights came up, and people were preparing to leave!