O'Wisp first appears in McBoo's Mansion Wii as a villain along with Tranzformez. He is revealed to be O'Lantern's flame and was originally controlling him but was removed from his body because he was making O'Lantern evil. O'Wisp then hated O'Lantern and wanted to destroy him ever since.
A while back, in his childhood, O'Lantern was evil and controlled by a flame inside of him, O'Wisp. He was soon removed by doctors because he caused to much damage. O'Wisp wanted revenge on O'Lantern even since then.