Castles In the Sky - The gang is devastated after their tree house collapses. It was the best place to hang out in the whole world. Can architect Frank Gehry get them to agree on a new design and help them to rebuild? Tipping the Scales - Everyone in Arthur's chorus group is excited about their upcoming performance in Crown City. Everyone knows nothing beats that post-concert cheesecake at Finklemeyers! But when strict Dr. Fugue replaces fun Mrs. Krasny as their teacher, the gang worries -will music class ever be fun again?