Zac had the shed door open because he was getting out clippers to trim some bushes when Alice went in it and saw her red car, which we hadn't gotten out for a while. She immediately wanted to ride it. It was the first time Simon saw the car, and, because of his great love of anything with wheels, it was almost unbearable for him to see Alice riding around in the car and not him.
I soon convinced Alice to give Simon a turn, and offered to let her wash the car while Simon sat in it. Alice loves washing things, so it was a win-win, if you just overlook the reinforcement of stereotypical gender roles.