How Miss Fortune's Double Up Works

http://imgur.com/a/wpBTQ

Mechanics raised in discussion: 

• "Behind" is relative to where MF is standing in relation to the target.
• While it doesn't prioritize champions, the random target selection might be weighted towards champions. This is pure speculation.
• I'm 90% certain that anything between the primary target and the bounce target will take the damage instead, kind of like Cait's ult. Needs further testing to be sure.
• Phreak is fairly certain that the bounce target is decided when the ability is cast, not when the primary target is hit.

Source: www.reddit.com/r/leagueoflegends