there are no known planets in our universe that are perfectly square in shape. Planets, including Earth, generally have a spherical or oblate spheroid shape due to the force of gravity acting on their mass. Gravity pulls matter inward, causing it to compress and form a roughly spherical shape.
However, it is worth noting that there is a wide variety of planetary shapes and structures in our solar system and beyond. Some planets may exhibit irregular shapes or have prominent features that give them a somewhat square-like appearance, such as sharp edges or flat regions. For example, the dwarf planet Haumea, located in the Kuiper Belt beyond Neptune, has an elongated shape with a flattened and somewhat square-like appearance due to its rapid rotation.
Furthermore, exoplanets (planets outside our solar system) have been discovered with diverse characteristics, and it is possible that future observations may reveal planets with unusual shapes or structures. Scientific exploration and advancements in astronomical observations continue to expand our knowledge of the universe, so it is always possible that new discoveries could challenge our current understanding.