It would be very interesting to go back to around 1050 - 1150 to see how people began conceptualizing and trying out different ways of playing the sport that we now know as Quidditch. I would love to be involved in the trial and error process of figuring out the configuration of the sport - bouncing ideas (and different sized and shaped balls) off of each other, spending hours out in the fields and finally returning home to dinner absolutely famished and exhausted, yet excited to try out new tricks and formulate ideas for the next day's play!
A bonus would be to immortalize myself through some form of quaffle trick or broomstick maneuver.
