The story opened with Arthur finishing up his invitations and going to school to hand them out to the boys and girls, who were sure to come. Then, he proceeded to hand one out to Muffy, who replied that she's having a birthday party. Arthur and Muffy both get surprised because they were born on the same day. As a result, Muffy said that the Saturday which Arthur had his party on, it was also the day she would have hers. They couldn't reschedule nor postpone their parties. Because a lot had been planned already. The classmates then discussed about whose party they could go to, and struggle to figure it out. After getting some gifts and more decorations, Arthur met up with Francine a few days later to tell her all about a solution to the problem. Then, they write invitations and deliver them to everyone's mail-box, and a special one goes to Muffy, telling her about a present too big to fit in a box, so she must be at Arthur's house to get it. Everyone makes it there, and they all surprised Muffy by having both parties at the same house. Muffy said that it should happen every year (saying, "Maybe we must do this every year".). Mrs. Read said, "But next year at your house". The story ended with Francine giving Arthur a bottle labelled "Spin the Bottle", which she had been pestering him about earlier on.