The Yellow Sky Means Age Swap

Jon stared out his window, waiting to see what color the sky would change to, so that he could get this experiment rolling. And after a few seconds, he watched as it became a brilliant yellow color. From reading the Charlie story, he knew what *that* meant: age swap. He left his bedroom in a hurry to try out his new ability before the sky returned to its normal color. But in his mad dash to leave his room, he accidentally bumped into someone and immediately swapped ages. But who did he bump into?