Jack's backyard clubhouse is a place in Jack's backyard. It is where Jack, Mary, and Mel hang out and play musical instruments.
Jack's House
Known residents are Jack, Jack's mom, and Mel. The interior of the house had only one appearance, in the Groundhog Day episode.
Jack's preschool
This was where Jack got his education.
The Giant's House
This place is located high up in the clouds. The Giant and his Wife live there, and Jack, Mary, and Mel met him there as well in the last episode of the show. It is implied that the trio visit him frequently, "to make up more songs".
