S06E18: Octi Gone

Professor Utonium is hosting a party for all the rich and famous people in Townsville, so Bubbles makes sure that she is the most beautiful of the girls by continually grooming herself. While doing this, she notices one of Octi's legs poking out from under the girls' bed, so she goes to pick him up to find that all that's there is one of Octi's legs! After waking up from the shock, she vows to exact revenge on the person who 'killed' Octi.