Gaseous ball

A gaseous ball was a celestial body inhabited by a humanoid species. As it was not actually a planet, gravity was constantly shifting so that up was sometimes down and down was sometimes up. The Eleventh Doctor found it confusing, but the natives had learned to adjust to it.

When the Doctor arrived on this world, he immediately fell up and crashed into Fariah Jazbloom's art, angering the artist and patrons. They chased the Doctor through their city, but he eluded them and, after realising the nature of their world, offered to make it the same as any other world. He departed after they turned down his offer. (COMIC: Run, Doctor, Run)