There are 2 types of Pete found in the game.
Pete will walk around sluggishly back and forth. Upon spotting Mickey Mouse, he will laugh, throw back his fists and slam them down. He will laugh again if his attack is successful.
Shell Pete will sluggishly move back and forth, though unlike regular Pete, a large, spiked shell covers his back from any direct attacks. Upon catching sight of Mickey, they will lunge in the air in a spinning motion, making them invulnerable.
The only way Mickey can defeat them is by spinning into them, which will cause them to reveal their other side. Mickey can then safely defeat them by bouncing off them.