Krook is a very annoying enemy, because of what he can do with those big hooks replacing his hands: He throws them like a boomerang . It may not sound that dangerous, but if you're in an enclosed space, like those found in world 6-2, or "Castle Crush", Krook's danger factor jumps up greatly, especially when combined with more Krook's and other kinds of enemies. Krook is also a big threat in world 4-3, "Bramble Scramble"