I don't know if this counts as 'funny' per se, I certainly didn't think so when it happened, tho' it has become a favourite 'wince making' story in the decades since.
One afternoon, in the far gone days when I was young and full of vim and vigour, I was sparring with one of the local Shotokan guys in their class at my university. I was Lau Gar Kung Fu, slim. quick and wiry. He was huge and strong and loved making his blocks
hurt. We were going at it pretty full bore and I was getting tired of the bruises I was getting on my arms trying to land something on him. So I switched to my more preferred style which was to attack with my legs - stronger and more reach after all, if rather slower.
Same result except this time it was my legs getting bruised rather than my arms.
So I hatched a plan to disrupt his defence with an axe kick to the head, steeping in on the descending foot, turning as it touched the ground to give him a rear elbow in the gut, with my moving weight behind it, to think on.
Sadly, as with all plans, this one did not survive contact with the enemy.
Instead of his stepping back to avoid the descending heel as I had anticipated, he committed the grievous sin of
leaning back out of the way. So my heel missed his forehead ... and his chest; the strike continued down towards the floor ... where the "sadly" part comes in is that it ever-so-nearly missed him entirely ... but not quite.
My big toe 'twanged' a certain pendulant part of the male anatomy as my foot flashed to earth. Result? 6' 3" of muscled, highly trained martial artist transmogrified into a puddle of jelly on the floor. Cue effusive apologies from me and concerned chortles from the rest of the room.
As I say, not funny at the time but certainly a memory that raises a rueful smile

.