Peter had forgotten something.
Just as he got what he had
Peter had forgot that his family was having his cousin family said that they were gonna be there for about 2 months. His cousin's family are as follows: Jake 40, Jasmin 38 and she is breastfeeding, Melissa 20 and has a 1 yr old daughter Tiffany, Timothy 17, Megan 14, Daisy 12, Mathew 9, James 5, Regina 4, & Amy 9 months.
Peter figured that if they were smaller then his feet they wouldn't go on.
Peter hadn't realize it when he pick up a pair of shoes that he hadn't grabbed his but that it was and then asked if he could try them on?
He had been curious and decided to try the shoes. He would not only swap the shoes but the spell changed reality so the person becomes him and he them. The spell had also had it where he can't swap back until he has actually walked a mile in them shoes. Which meant he depending on which body would be stuck in that body, which means he has to go 5,280 feet before able to swap into another person or become himself.
So if he decided to become someone really young he could be stuck for quite a while until he learns to walk and if he did his grand parent it might be the same.