We stumbled upon either a 2" or 2.5" floppy early in my college career. None of us had ever heard of such a beast - it was a bit like alien tech landing in our laps. We figured it was "the future" and that smaller floppies would see mass-adoption, as some sort of CD-killer.
Then our professor destroyed our dream world and said they'd died off in the 80s. (And then wisely predicted flash-like memory would kill off all of them.)
There's a wide range of weird floppy sizes. Perhaps one of the best known was sold for the Amstrad PCW - a popular word processing system. (This machine kept CP/M alive during the 80s and into the early 90s.)
Then our professor destroyed our dream world and said they'd died off in the 80s. (And then wisely predicted flash-like memory would kill off all of them.)