All it took this morning was Joseph finding a party hat from Julia & Sara's birthday for him to decide we needed to have a celebration right away. He even went and chose a present and asked me to wrap it for him. So when he went upstairs to help Papa feed the cats, I ran with it. Of course he had forgotten all about it 10 minutes later, so it turned out to be a surprise party.
What present did he choose for himself? Trains. No surprise there.