User blog comment:Kassyndra/What is champion skin you want most to happen?/@comment-26460333-20150605175612

Oh, just thought of this, but what about:

Treant Malphite and Monolith Maokai?

They switch materials, so Malphite is wood and Maokai is Stone.

They are both elemental buddies after all, so I think it'd be cute. xP