Originally Posted by Fat The Reptile
You forgot Mew, and you have overlooked one major pattern they all share - Outside of Manaphy (And Shaymin, who I shall add because it's a 600 BST 100 all stats legendary "pixie"), they are all (part) psychic-type. This means that if Gen VI includes a "pixie" legendary (which it most likely will - all generations have included at least one), it will most likely be Psychic or part Psychic-type. As for the other typing, I am not seeing any relation between them, or how it's more likely to be Electric-, Dark-, or Fighting-type
Well, first of all, when posting, I totally forgot celebi was Psychic, so I didn't not that, but that's a good thing to put down.
Similarly, I was thinking of primarily Jirachi as Psychic, in which case fighting and dark would fit, but now I am realizing that was not the smartest thought.
With electric, however, that COULD be considered one of the starting types (red/blue/green/YELLOW), so Electric/psychic pixie sounds like a possibility to me. I'd love that, as I am an electric fan.
And also, the reason I left out mew:
I originally thought celebi was 3rd gen. I didn't realize my mistake until halfway through. So I was thinking they'd only done "cute" legendaries (not including mew) since gen 3, but when I realized that was wrong and changed it I didn't think to go back and add in mew.
EDIT: I edited the post, updating it.