Really into the idea that Nico is actually the son of Pluto not Hades, and that's why every single person at Camp Half-Blood, even the supposed mentors, act so hostile towards him, no matter how much he works on their side, and yet nobody at Camp Jupiter really seems to mind him, or oppose Nico all that much.

Also, why him and Hazel inmeadiatly click together, and he's able to find her in the Underworld pretty easily, even though technically all Phanteons are said to have their own afterlife, so Hades's realm and Pluto's shouldn't be the same