Right after your teams have completed their 2nd or 3rd retro, and seem to be getting the hang of this, it’s time for this variation. Before calling them to begin, run around and swap some of their tennis balls for yellow ping-pong balls, or pickle balls, or even giant yellow pillows (pretty much anything you can do as long as it has a different size and/or weight). Then order them to begin. I guarantee you’ll get protests. You may hear cries of “Scope Creep!” At this point, simply explain “Not every backlog item a team works on is the same size or scope, and quite often after work has begun, the team realizes the work is bigger or smaller than originally estimated. This is not additional requirements! This isn’t scope creep! It represents your team learning more about the stories you’ve accepted. Please begin!”, and start the timer.
Origin: Partially because of the crumpled-paper as manager task scenario, I noticed something interesting. Similar to juggling, the players started getting accustomed to the heft and size of the tennis balls. Their repeatable pattern seemed to be dependent on the uniformity of the balls. So when they suddenly have to recalibrate to toss a lighter, smaller ball, or even a lighter one with the same size, or a bigger, heavier ball — the impact on their rhythm is immediately observable.
Reality Check: The truth is, this variation is more realistic than you may recognize. Teams are always finding surprises about the stories they accept into sprints. Good teams will adapt and do their best. We are illustrating this point here. In general it helps to find any kind of ball you want, as long as it’s yellow. I’ve even given them a few Nerf footballs.