controls for player 1
    Arrows - move (in battle and overworld)
    Enter - interact (overworld)

controls for player 2
    WASD - move (in battle and overworld)
    Z - interact (overworld)

you can change the Enter and Z key interact in the Undertale settings: "P1 can interact with ..."

if you want to play with joystick:
    you use a program called JoytoKey ( Joytokey.net )
    Its lets you convert joypad inputs into keyboard inputs (basically you can setup the second player controller D-pad/Joystick to press the WASD keys to control its character). 


