In this video, MetaBallStudios compares the sizes of various fictional planets from film, television, books and video games.
From MetaBallStudios:
Many planets are missing (Caprica, Planet 4546B, Planet Miller, Xandar, Kerwan, Namek, Planet Vegeta, Vekta, Spherus Magna, Secunda and Masser, Pandora, Magrathea, Polus, Typhon etc, etc, etc) due to lack of information or impossibility of measurement, they could not be included. I’m sorry. Including habitable asteroids, moons, and artificial planets (but shaped like a planet.) There may be some exceptions like the Discworld.