Backyardigans Birthday Party Supplies. The best Children's Birthday Party Ideas start with a great birthday party theme, so for a fantastic Backyardigans Birthday Party, start with our amazing selection of Backyardigans Birthday Party Supplies. The Backyardigans makes for a great party theme idea and for an amazing Birthday Party! Have a party to remember this year with a terrific kid's birthday party theme featuring The Backyardigans! Great Birthday Parties start with Great Birthday Party Supplies!