So many things I love that people have said already.
I'll just give my thoughts on the Kirby situation. I doubt he's a robot since he has that moment with Donnie where they chimed together about using tape voice backtracking or something. Robots dont have that kind of logic way of thinking, they just do the task and be done with it.
And when he hugged Donnie and went out carelessly... That is very odd. Like he had no fear at all. Was it because he trusted Donnie got everything under control (Nah.) or because it's all part of his (and Kraang's) plan?
Finally when he found and hugged April, his eyes gleamed dangerously. I was expecting a red light glare if it's a robot, but nothing like that happened. Did he have an agreement with Kraang to use his daughter for the planetary mutation? Or maybe mind control? Seems plausible.