FYI, if you connect via IPv6 then you can watch in colour :)

Pity ^S/^Q don't work for pause/play. ^C/^Z also don't seem to work for quitting. I wonder what's preventing these keybindings from working. Very cool regardless.

The fact that Telnet is actually a protocol, and a weird one (mostly because it's ancient and actually predates UNIX). I believe the reason is that those keypresses are not interpreted by your terminal but instead sent over to the other side to be interpreted there. Obviously, they don't do anything there.

With "nc towel.blinkenlights.nl 23", on the other hand, they would work.

Ah, reminds me of messing with my friends by piping the output to a write message on their terminals. Super annoying because it just scrolls through the terminal frame by frame.