fair warning, this is very glitchy (don't hide in a locker or you will be stuck forever) and also items don't work for some reason
click ` on your keyboard while 2 controllers are connected and run the command CreateNewPlayer 1 and restart your run. It is seriously that simple.
one thing to note, any gui that is important to your character will only be accurate to the person on that side of the screen (health and stamina)
also, you can use the command SSSwapControllers to switch who the top and bottom players are
uhhhhhhhhhhhhhhh oh yeah and i hate miss Bloomie