I'm afraid that's classified information, and if I explain the secret of longevity to you... well, I'd have to kill you. And as fun as that would be, I'd really rather not put up with whatever sort of punishment Thing 1 and Thing 2 deem appropriate in retaliation for that. So, believe what you want. I know who I am, and if I cared about people knowing who I was in this day and age, I wouldn't have gone through the trouble to ensure the world believed I died in 1943.