Here's some fun headcannons have been brewing in the back of my mind:
Earth absolutely dominates at monopoly
Monopoly has been banned from the solar system
Jupiter has and will read for years on end
The dwarf planets play hide and seek in the Kuiper Belt (they have accidentally found Neptune many times)
If Uranus wants to talk to Neptune, he asks the dwarf planets to find him (bribing them with art for their latest campaign)
Saturn definitely knits, making things for his and Jupiter's moons.
Ceres watches Mars from the asteroid belt (Mars knows this and is scared)
The rocky planets sometimes have races (Mercury always wins)
Earth is very competitive, yet Venus is the sore loser (Monopoly was banned because of him)
Sol likes to watch his planets have fun
Venus tried to chase Mercury once but he is FAST
Venus deep down loves his name
The planets actually love Sol's jokes, some of them are actually really good