Tales of the Legion of Super-Heroes in "Target--21 Legionnaires"
Soon after Invisible Kid is elected leader of the Legion, they are attacked by Doctor Regulus.
Regulus steals the Legion Club House and is responsible for Sun Boy losing his memory.
Regulus is defeated by Sun Boy, its then revealed that it is Regulus who is responsible for Sun Boy gaining his powers.
"Get Hip to Old Folks!"