Pete is a Skeleton who helped SMG4 and Mario get out of the pit in SMG3's lair when they were about to get crushed by spikes in the video SMG3's Gauntlet of Gloom. Unfortunately, Pete did not make it out of the pit and was crushed.
Pete later appeared again in SMG4: Stupid Mario Odyssey, but Mario doesn't recognize him. He is seen at Little Bone Village as the king of that village which means he survived the pit and did not die but later gets eaten by a Dinosaur.
His latest appearances have been his cameos in The Mario Channel: Mario's Challenge, SMG4: Stupid Luigi's Mansion and SMG4: The Movie Audition.