[xenadu02]

Ah this one was so long ago I forgot about it.

The realization that (on DOS) "copy con file.txt" as the world's worst text editor or "copy file lpt1:" was treating physical devices as files. Everything on the computer was arbitrary so you could make anything behave like anything else (for some definition of behave like)!

Not a great insight I'll grant but a key one that everyone has to go through to be any good.