Arthur can't wait to hand out his birthday party invitations. But it turns out Muffy is having her party on the exact same day! Buster and the boys decide to stick together for Arthur's party, and Muffy's convinced the girls to go to hers. Arthur and Francine agree that it won't be as much fun without all their friends together. So they hatch a clever scheme to make sure Arthur and Muffy have the best birthdays yet!