Kruller appears as a purple ghost wearing sun glasses and police uniform. He has blue eyes behind his sun glasses and black hair under his hat.
Unlike other bosses, trying to attack Luigi directly, Kruller rolls away from Luigi cowardly and enters a room which only Gooigi can enter. He is also not a perfect guard because he should be watching all the shops, but instead, Luigi wasn't caught by him at all until Luigi gets into his room.
When Luigi enters Kruller's room, Kruller got shocked and tried to get away from Luigi by rolling into another room. He picks out a squirt gun from a box as a weapon. Only Gooigi can fight him. You can't flash him before you suck his sun glasses. While you are sucking the sun glasses, you have to dodge from the water he shoots or else Gooigi will melt. After the sun glasses is sucked up, you can flash him and suck him. Repeat the steps and he will be defeated.
- Kruller is the only boss who can't deal damage to Luigi.
- "Kruller" is pronounced same as "cruller", which means a kind of doughnut.