You do enough wrenching, you've got some memories (hopefully).
One sticks out in my mind, and it wasn't a boneheaded move on my part either. I was working on a TH350 trans rebuild in a '77 Chevy pickup. Long bed 2wd. Pretty easy. Had it up on jackstands, used the jack to lift the trans out and then back in. Had it all done, had truck running on the stands to check/adjust fluid levels, pressures, etc--all went well. After dinner (and time for the truck to cool), I climbed back under it to triple check for leaks in the normal leak places, e.g., pan, converter seal area, converter area, and extension housing. None found. While I was under it I happened to notice that the FRAME of the truck was buckling/bending where the jack stand was against it. I couldn't believe it and still don't believe how CHEESY those stupid trucks are built! Well before I could get out from under it, the buckled frame gave, truck fell, then of course with only 3 holding it, the load shifted, and fell off the other 3. There I was pinned under the truck, couldn't get out, no cellphone, couldn't get to the house phone, nobody to holler at. If I hollered and nobody heard me, was there a sound made?? LOL! Anyway it was on the wheels but it was still on me pretty tight. That day just happened to be my birthday. No big deal, I don't generally celebrate my birthdays anyway. The girfriend at the time, however, is different. She decided to surprise me for my birthday by showing up with steaks from the local steakhouse. 'Course there I was stuck under the truck just waiting for someone to show up. She had no idea how to use a floor jack but she learned real quick, got the truck lifted just high enough, I skinnied out from under it and checked for missing appendages, etc. The frame kinda laid across my belly and missed the ribs by not much and my hip bones by not much either, so was real lucky. Got some bruises, but no major injury.
The dude that owned the truck was mad about his frame, but as I showed him the bruising on my belly, he calmed down a little. Besides, it ain't my fault that the frame was a steaming piece of feces!
Most of the time it's the jack stands that fail but not this time. These were good stands with nice, wide steel pads so I was pretty confident with 'em. The truck? Shouldn't have happened. Dude that owned it got rear ended not a week after he got it back and they totaled the pile of junk. Good. I wish it'd have burned, so long as nobody was in it.