How Robert Downey Jr. got a shirt of Bruce Lee DJing into 'Avengers: Age of Ultron'

Warning: If you haven't seen "Avengers: Age of Ultron" there are spoilers ahead! Halfway through "Avengers: Age of Ultron," when it looks like The Avengers have their backs against the wall, Tony Stark (Robert Downey Jr.) begins to devise a plan to gain the upper hand with Bruce Banner (Mark Ruffalo). What he's wearing is likely to be the must-have T-shirt of the summer. As the two speak, Stark is seen casually wearing a gray tee sporting a shirtless, DJing Bruce Lee rocking sunglasses from behi...