Ahh, teenagers.

Parents joke all the time about the things they expect to walk in on at some point or another.

Some even dread the embarrassing things they'll catch their kids doing that they'll never discuss with them.

One dad in particular was so caught off-guard after walking in on his son, he never discussed it with him.

Reddit user "Aubamaw*nk" shared the story of when his father walked in on him having sex with his high school girlfriend when he was 18 in the "Dear Reddit, Today, I F**ked Up" subReddit.

The Reddit user explained that he and his parents had a good relationship. They were impressed with the girl he'd brought home, but everyone was still getting used to the idea of him having his first girlfriend.

"So basically, I had my gf over. She had met my family/parents and everything was good. My parents liked her. She liked my parents."

"I had never even had a girlfriend or anything before (at the time I was only 18) so my parents weren't completely used to their son having a lady over."

But on this particular visit with his girlfriend, the couple decided to push their luck a little bit, doing more in the then-18-year-old's bedroom than you should when your parents are home.

"Anyway, so we're upstairs in my bedroom and we start gettin a little freaky. Things escalate and we eventually start having sex. We were super quiet about it so that nobody would know."

And of course, being quiet or not, they were going to get caught.

Of course.

"...she's riding me, and my dad just casually walks into my room and essentially gets a full a$$ view of... my willy half-way up main street. He's so startled he makes one of those 'DOH!' sounds like Homer Simpson y'know??? He quickly turns away pretending like he hadn't seen anything. This all happened in less than 2 seconds."

Somehow, even in all the surprise, the Reddit user's dad covered for him when his mom asked what all the commotion was about.

"I can hear my mom downstairs say 'Honey? What was that?!'"

"My dad, god bless his soul, replies 'I... uhhh... stubbed my toe...' in the most defeated way possible."

But that doesn't mean things weren't awkward after that.

"My gf couldn't look at my dad the same way again."

"I haven't talked about it with my dad ever."

"edit: I still laugh my a$ off telling this story to people."

Fellow Reddit users thought this story was hilarious.

Some shared their own embarrassing stories, but most took a moment to commend the original Reddit user's dad for playing it so cool.

"Good on your dad for being so chill and also not yelling out to your mum what he had seen" - FreedomPeaches

"As a parent, maybe don't walk in on your kids when they have their gf/bf over? I mean they're teenagers wtf do you expect them to do, sit around and talk?" - jojo_31

"Had a similar experience in HS. Girlfriends dad just said 'Oh, Jesus' and left. About 5 minutes later he said through the door that I had to leave in 15 minutes."

"Of course, the moment was ruined and we were both just sitting there mortified, but I thought it was pretty rad that her dad was giving me some extra time to finish boning his daughter." - BreakfastBeerz

"My ex's dad happened to come home while we were both in the shower."

"Turns out he was less mad about me railing his daughter, and more about the fucking water bill, and oh boy did he lay into me about it."

"Come to think of it, he may have been in denial about the whole shebang." - UrMomLikesMine

It is kind of admirable that the dad was able to turn a story so quickly. But this probably wasn't the first time he and his son had exchanged an embarrassing moment.

Hopefully he at least has a funny story that he can laugh about to himself every once in a while.