Is there anything more soul-crushingly embarrassing than being caught having sex by your parents?! Probably, but it's hard to think of anything that rivals the dreaded creaking of a doorknob only to reveal mom or dad aghast at your sexual activity.
While shenanigans of this nature are the subject of many humiliating movie scenes, they also go down in real life, and there are people who survive to tell the tale.
Mom walked in on me face deep in my junior prom date. The worst conversation of my life came shortly afterward.
Happened twice. First time was my brother when I was like 17-18. Wanted me to move my car, so he walked into my room. Blanket was over us, but I was on top of her when she walked in. He just said "Sorry." and closed the door. He profusely apologized later that day when I saw him again.