A good way to feel old is to ask someone who their favorite Justin Timberlake is. The singer/actor/dancer/comedian has been at it from such a young age that he's actually gone through many iterations of himself — and some of us have been there from day one. You may know Timberlake from his days as a member of the Mickey Mouse Club, or maybe as the boyfriend of former costar Britney Spears . Or maybe, somehow, you're just meeting him now thanks to his hit song "Can't Stop The Feeling" from Trolls.