Until you run it.
Then this happens:
Rainbow propelled cat jacking your desktop ahoy!
The music from the Nyancat website plays in the background too (you know, just in case you still thought the above was a normal feature of Windows. It wouldn’t surprise me though).
Getting rid of it involves not panicking (always a good first step) and opening up Task Manager:
As you can see, Nyancat.exe has a habit of punching your memory usage in the face with a brick, so you may well find the PC gasping and rolling around on the floor a little as you kill the process off. While this is more annoying than malicious, it’s worth noting that a quick scan of search engines reveals Nyancat batch virus coding taking place and some other nasties floating around using the pretence of “strange yet friendly rainbow cat”.
Stay safe, meme fans…