In his mad dash to leave his room, Jon accidentally bumped into his little brother Mikey and immediately swapped roles with him.
Jon watched as Mikey walked into his room, wearing a smaller version of what Jon had been wearing.
When Jon looked down at himself, he saw that he was wearing a larger version of what Mikey was wearing. Certainly, he would be a laughing stock, wearing a digimon shirt like that to the high school.
He walked back into his room and got a shock. His bedroom had changed to look like Mikey's room. Despite belonging to a high schooler, the room looked like it belonged to a ten year old. And he had a feeling that Mikey's room had changed to look like Jon's. All of Mikey's toys were there, as well as his comic books.
As Jon tried to process the changes in reality, he noticed the sky returning to its original color.