I accidentally acquired /u/Polsaker's IP and started scanning his ports for fun. The scan came back with the usual ports open, except one that caught my eye - Port 4242, which I have never seen before. I Googled it, and there are a number of services that run on Port 4242. A couple of them are trojans, a couple are games. In Polsaker's case, it is open because the Quassel IRC client uses it.
There is another use for Port 4242 though. Reverse Battle Tetris. I decided to look it up to see what the game is like, and discovered something very unusual. It doesn't exist. There is literally no mention of Reverse Battle Tetris anywhere on the internet, unless it is mentioning that Reverse Battle Tetris runs on Port 4242.
There is only one explanation for this. Certain ports are designated for specific purposes, such as 80 - HTTP, 21 - FTP and 22 - SSH. These ports are official port designations. Other ports though, do not have any specific purpose, and are only used to run very specific services. These are unofficial port designations.
The only possible explanation for Reverse Battle Tetris is someone made it up. They edited Wikipedia, and other sites copied over the information, saying that Reverse Battle Tetris runs on Port 4242.
If you don't believe me, here is the port. Now Google Reverse Battle Tetris and try and find a single shred of evidence that it is a real thing.
Polsaker found the original mention of it, and it appears that someone in Hasselt University first made the Wiki edit in 2012. From there, it spread over the entire internet and now everybody is convinced that Reverse Battle Tetris uses Port 4242.