@hex Seems like this was what I was thinking of: https://en.wikipedia.org/wiki/SuperDisk
However, I misremembered, no 120MB on regular floppy, but up to 32MB:
It has double the capacity of the LS-120 and the added feature of being able to format regular floppy disks to 32 MB capacity.[3] However, this higher density comes at a price – the entire disk must be rewritten any time a change is made, much like early CD-RW media.