or Rapunzel. They're both eccentric and like to help others :)

^ I agree. Their personalities are more quirky and unique. :)

Both are "outcasts" and seen as loonies, so would be able to relate to each other -- and even though Belle is kind of similar to Hermione in some ways and the two don't often see eye to eye, I think Belle is a more accepting & imaginative person than Hermione and would probably get along with Luna well. I'm sure Belle would be sorted into Ravenclaw too (unless she 'chose' not to) which would help.

^ agree totally

and Ariel

Rapunzel would get super excited about Crumple-Horned Snorkacks, I can see them going on holidays to find them together.

I think Luna needs someone more practical to hang out with...

I can't believe "....who's Luna Lovegood...?" is winning!