SUPER CRAZY RHYTHM CASTLE

Easiest way to get this is to play Versus Chaos with two players. Have one player 1 pick up the egg on their side and drop it on the other player's side of the field, then player 2 picks up the egg and puts it in the egg cup at the top of the field. It'll activate and attack the other player awarding the achievement.

Then do the same again but reverse the roles for the other player to get the achievement too.