Justice League Teaser Breakdown: 20 Things You Need To See
9. The Flash Shows Off His Powers
Despite the fact that all of his screens are turned on and have pictures of him on, and his costume is hanging up, Barry claims innocence, so Bruce tests his powers by throwing a Batarang at him. As you do.
That leads to a spectacular slow-motion shot of Barry dodging the missile, complete with lightning flashes (he's not going to be very good in a stealth situation)...
And the slow realisation on Miller's face that it's actually Batman throwing something at him is just genius...