Expressing Excitement

So I’ve been trying to set up playdates for Tornado E, so that he doesn’t maul children and get into their faces when they just want him to take a step back and give them a little breathing room.  Last week I succeeded in securing a meeting at a park with a mother of the twins Tornado E likes so much.  When I told Tornado E he had to get ready to go to the park and meet his friends, he let out a high pitch squeal, which probably took off a year of my hearing, and ran off to get ready.

My question is: When did my four-year-old little boy turn into a teenage girl?