Beautiful Giants

Back when they were casting Supernatural, Jensen Ackles auditioned for - and was offered - the part of Sam Winchester. Later after meeting Jared they turned around and offered Jensen the part of Dean instead. Ultimately convincing him by saying wouldn’t he rather be Han Solo than Luke Skywalker?

Coincidentally, Jared Padalecki auditioned for Jason Teagues on Smallville but didn’t get the part because they didn’t want someone that was taller than Tom Welling. Jason Teagues ended up being played by Jensen Ackles.