Used to call asleep with arm under my head face down. Arm would be totally numb and it'd wake me up. Flip over onto my back and hit myself in the face with my giant limp noodle arm.

This can actually cause permanent damage in rare cases. Generally when you've been drinking, which is why they call it Saturday Night Palsy.

Also, as a middle aged adult, I can tell you that sleeping in the standard "arm under the pillow" position which produces this can also cause very serious degenerative shoulder damage which can result in needing one of those surgeries where you get one shot at it and there's like a 5-10% change of it failing and you living the rest of your life in constant pain.

I've done that to both arms simultaneously. Geez I hope I don't gotta get up for an emergency