Mulberry 7

Mulberry 7 as seen from space.

Mulberry 7 is the 42nd stage station planet on the Galaxy Highway, best known for its clams. However, nothing else is known about this planet, as Robby, Hatchi and Ikku land on Mulberry 8 instead.
This planet was mentioned in episode 8.

Trivia

Mulberry 7 is named after Kuwana, which was also a station of the original Tōkaidō – kuwa means mulberry and 7 comes from nana (seven in Japanese). Nowadays Kuwana is known for clams.