Use W to jump, A to go left, D to go right, and S to crouch. For second player it's I to jump, J to go left, L to go right, and K to crouch. For third player it's T to jump, F to go left, H to go right, and G to crouch.
I had a LOT of inspirations. Sir Harold as Gigant Edge, Zak as Squashini Beezus as Meta Knight Hunter as Duck