If you plug in the second controller and play solo mode, then go up to sonic or another character and you can move around with them and kill people. So you can play two player on solo mode!
NOTE: You can not play with dooms eye, and you can not pick up guns.
Heres another one
Sometimes you hear the soldiers say some random stuff? Well sometimes they will say Yugi Naka is alright! Yugi naka is the creater of sonic.