Probably the wrong forum for this, but maybe a few can appreciate it.
About 35 years ago we had a staff meeting interrupted in the middle of the afternoon by a noob systems programmer who came in and said, very sheepishly, "I believe I just deleted SYS1.PROCLIB" -- it may have been SYS1.PARMLIB -- too long ago to remember...
Reminds me of when I worked for HP in the mid 90's and we had to take a trip to one of their facilities in California. In the data center was an old HP 1000/RTE realtime computer they still used to run some of their systems (facilities systems I think).
We were all gawking at it one day, we'd never seen anything like it before, at least still running in production. I remember it had a punch tape reader on it, but I don't think they used that anymore. There was a large rack of tape reels against the wall, and it also had some disk packs (mag packs? I forget the exact terminology, it was a little before my time) attached to it.
It was humming along just fine until one day...
We were in there setting up some racks of servers for a Windows NT installation, and one of our guys had a raised floor tile removed (one of the few times I remember seeing a raised floor data center in California), and he accidentally kicked a connector loose from one of the disk packs, and didn't notice at first.
Later, some sys admins rushed in in a panic. Evidently, we had crashed it hard, the guy who knew the most about it had retired, and it had run so long without incident, nobody else knew much about it.
The next day, they had brought the retired guy in to help out, and he was PISSED. The guy who knocked out the cable apologized, but the guy ripped him a new one. I guess they got everything running again later in the day.
Our last day there, we noticed one of our NT servers was having problems, and when we started checking things out, found some of the Fibre Channel cables had been unplugged between the server and the SAN switch. Payback I guess, but we never found out for sure.