Question you might ask: 1. Why does Sonic.ROTTENEXE have Slenderman type Tentacle thingys behind his back?
Answer to Question 1: Well It's because Sonic.ROTTENEXE is an Inspiring Character and His true form is something you might experience that has Tentacles when the Game Releases so Wait until the Game comes out.

Question you might ask: 2. Why is Sonic.ROTTENEXE an Inspiring Character?
Answer to Question 2: It's because he's my own Creation, Duh.