In school when I was a kid (maybe 8 or 9 at the time) I was talking too much in class and the teacher got fed up and said to me "Go outside and find yourself"...I didn't quite get what it meant at the time but I also could tell she didn't mean it literally either, but that didn't stop me from coming up with the hilarious idea to walk out of the room and start yelling "Matthew, where aaaarrre you!". I could hear my class and the neighboring one laughing from outside
Once when I was 15 I wanted to impress my friends at a local park so I tried to do a Super Mario wall-jump off a particular surface that wasn't as sturdy as it looked (it was a wire mesh used on a large soccer goal that had been put aside by the park carers) I ran up to it and prepared to strike it, then leap off it to go even higher like a popular Mario move, only instead it collapsed upon impact and I landed hard on the dirty ground. It hurt like hell but my friends couldn't stop cracking up at such a failed stunt. I then laughed too since I could only imagine how funny it would have been from their point of view
I've encountered many hilarious memories in my lifetime. Half of which being funny videos on the internet. One particular memory took place in a hospital where I was asked if I had cigarettes on me. Why did the person ask me that? I wreaked of smoke. Though, that's not the funny part. The funny part was when I was lectured by a bystander for smoking when I've never smoked a cigarette in my life. My parents smoke, not I.