Speaking of URLs that do fancy stuff on the terminal, I once stumbled upon this one from textfiles.com, it's essentially a short animated movie on the terminal using VT100 terminal codes, all served from a URI. On modern systems you can use rate-limiting to watch it:

curl --limit-rate 1000 http://textfiles.com/sf/STARTREK/trek.vt && reset

(the reset is there because it might mess up your terminal)

Other terminal-powered URIs:

curl cheat.sh/tar (gets examples on how to use the program after the /)

curl wttr.in/berlin (gets weather info with terminal formatting)