I remember a kid's book I read between 10-13 years ago. The cover was had a lot of bright colors. I believe the main character was a wizard who was called to go fix people's magical mistakes. There was one mistake where two sisters pulled a wishbone and one of them wished that her sister would swell up like a balloon and her sister's boyfriend would turn into a dog, while the other wished good things for her sister and her boyfriend. But the wishbone had broken straight down the middle so their wishes were turned back onto themselves so the jealous one had swollen up like a balloon and her boyfriend had turned into a dog, and the kind sister and her boyfriend were experiencing more happiness then before. The wizard made sure that the jealous sister had learned her lesson before he undid the wish.
I feel like there were other shenanigans that the wizard had to undo, but I don't remember what they were.
I feel like there were other shenanigans that the wizard had to undo, but I don't remember what they were.