Board Thread:Naruto Discussions/@comment-1018594-20160409062530/@comment-28483245-20160619130556

Here's one:

Indra's Mangekyo has a spiral pattern. It looks identical to the ripples in the Rinnegan. I think that is a clear connection: his mangekyo looking similar to a rinnegan in shape could come from the fact that he is a direct descendant of a person who wielded the rinnegan(Hagoromo), or that he is a grandchild to a person who wielded the rinne sharingan, which as we know looks similar both in color and in shape to his mangekyo.