Risc OS Software that Made Your Jaw Drop

Didn’t the Zansi terminal do something similar, as well as somewhat freaky looking output?

Unsure. I used it for a bit back in 1995 until I picked up a new IDE card for my original A3000 (still running from floppy at that point!) which had a copy of Hearsay on it. ZAnsi never actually screwed up on me though, has to be said.