a few years ago i was laying in bed with my wife (fiancée at the time) trying to sleep, as you do. we were both mostly asleep but still just awake enough to be aware of the outside world
and uh, i was a bit gassy. and we got over the "i can't fart around my partner" phase of our relationship pretty early and also i was tired, so whatever
my wife, still half asleep, then rolls over to me, smacks my butt and says "go back in"
a couple seconds pass as we both process what she just said, and then we start laughing so hard that we woke ourselves up completely
we still occasionally quote "go back in" to this day