I just had this idea for a Down B move for King K. Rool. Let me share it with you.
Down B: Play Dead.
When Down B is continually held down, K. Rool will do what he can do best, play dead. When he does this, he will be motionless and will not be able to do anything, but he cannot be damaged at all, making him completely invulnerable to attacks. He can still be moved around a bit. K. Rool will wake up after some time. Also, when the move stops being used, but is used again shortly afterward, K. Rool will play dead in a shorter time than the last, and with that, he must wait for a while before he can use the move again at the full amount of time.
Note: If King K. Rool is on his last life, or has the least amount of KOs in battle, you'll see the credits roll on by. They move pretty fast, though, and can only be seen easily when one pauses the game. Also, this will happen once per battle.
So, what do you all think?