I just remember Madara's real eye went to Nagato and when he died Obito got back the rinnegan and transplant the eye in his eye so shouldn't he have the power to switch the it to the sharingan and then switch it back rinnegan. Just wondering.
You know what I find more puzzling? ... Madara gave HIS eyes to Nagato... so Nagato's eyes are Madara's eyes. Then Tobi took Madara's eyes... YET... somehow this ONE pair of eyes... at the time of the war is possessed by Madara, Tobi AND Nagato lol. It's like it's getting dished out to just anyone.
In fact the whole ocular transfer seems to be some kind of mystic magic... Itachi apparently transferred his mangekyou powers to Sasuke's eyes just by staring in his eye. So then later, Sasuke unlocked his Mangekyou Sharingan following a moment of extreme emotion and had Itachi's Mangekyou powers. Then, apparently to get Eternal Mangekyou, Itachi's eyes are transplanted into Sasuke's... But then ... isn't Sasuke just having his mangekyou eyes gouged out and Itachi's mangekyou eyes put into his. Doesn't that make Sasuke's new eyes just Itachi's Mangekyou eye?
Or is it because, Itachi's mangekyou eyes have been put into Sasuke's previously mangekyou-eye-hosting eye sockets, it allows him to access EMS abilities?? Or is the mangekyou stackable. Like Sasuke's eyes remain in his sockets, then Itachi's gets added into it through transplantation?? But then, this also makes no sense.. There's only one eye socket for each eye and it's already being occupied by an eye. How can you add another eye in there? Does it just get mushed or squashed into the eye socket? It's all a bit mysterious.