Pft, you didn't take that theory far ENOUGH. You know who has lime green font? Jade. And she also gets her powers from Bec and the Green Sun. So obviously, this means that UU is the limeblooded offspring of Karkat and Jade.
Tinfoil hat Homestuck discussion is the best Homestuck discussion.
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You have no time to ponder such questions, as Link has just grabbed a Smash Ball.
http://backloggery.com/herodeltiempo/sig.gif