Twin Princesses of the Wonder Planet (ふしぎ星の☆ふたご姫, Fushigi-boshi no Futago-hime?) is a Japanese magical girl anime series about the adventures of twin princesses in Fushigi-boshi, a mysterious planet shaped like a hollow earth. It is based on a concept by "Birthday"" and produced by Nihon Ad Systems and TV Tokyo. It is directed by Jun'ichi Sato who directed the first series of Sailor Moon. Fushigi-boshi no Futago-hime originally aired on April 2005. A sequel titled Fushigiboshi no Futagohime Gyu! began airing in April 2006 and ended on March 31, 2007.