My nerd dream came true: 1) Open your Terminal in Mac OS X or Windows or Linux or whatever the hell you are running your toaster on. 2) Type telnet miku.acm.uiuc.edu. 3. Enjoy an endless nyancat loop in glorious ASCII.
If it doesn't work, make sure your terminal is in the correct mode (just select ANSI in the preferences and it will work) or type this:
TERM=ansi telnet miku.acm.uiuc.edu
I wish it also had music. [Thanks Karl!]