Trope-a-Day: City Planet
City Planet: Alas (?), none of the planet-sized worlds in the Worlds have yet grown to the point of being ecumenopoleis.
On the other hand, the subverted “small planet” version is definitely present: 1 Andír, in the Lumenna-Súnáris System, has been slowly hollowed out over centuries to the point where it actually is a beehive habitat/asteroid city filling all of the Ceres-like dwarf planet that it’s “on”. Or there’s the moon Palaxias in the Palaxias System that houses the IN’s Prime Base, which is similar and even bigger, except that it’s probably cheating when the majority of that hollowed-out space is spacedocks for really big starships in large numbers.