There is a secret easter egg where you can activate a virtual cat on a linux or a UNIX system. Though it is reported that it can hang your system in certain distros so it is best advised you save and close all your work and so on before attempting because if things go wrong, you may be forced to pull out the power plug.

To summon the cat, try the following command:

meow() { meow | meow & }; meow

If you see something like

[1] 583341
[1]+  Done                 meow|meow

Quickly up arrow and rerun the command untill you see no output. And after a few seconds the cat will appear on the screen that follows your mouse pointer. Very cute.

Update: This also works in Windows with GitBash