Not just on UNIX
For some years, I worked for a government contract for the tending of Data General minicomputers. There were a lot of machines and a lot of operators and analysts, so that it was probably inevitable that now and then somebody would
CDIR :
DEL #
Once I was that somebody. What I discovered early on was that the peripheral manager, :PMNGR, was early in the usual order of files and so one of the first to be deleted. But once it was gone, there was no way for the system to delete (or create) files. Owing to our loose discipline in cleaning up after updates, there was usually a copy of :PMNGR.x.y.z that one could rename, and from there begin the recovery. And I think that the CLI used a sort of breadth-first discipline, meaning that the subdirectories of root were not purged until all the standard files were. One did not want to run with an obsolete :PMNGR, so that one then had to go to the latest systape.
Then there was the customer's employee at a previous job who was working his way through the commands and utilities book one evening until he got to FORMAT. It worked as described, but not as he'd have desired.