Theoretically, the Kyuubi and Obito never met, but when he releases the Nine Tails, there is a moment of recognition.
Do you think that Madara did something like Orochimaru's body soul transfer technique and is hosting his chakra/soul in Obito's body?
It clearly says controlling biju needs ""time and knowledge and skill".
But i just thought of something we all took the nine tails saying "You!" as he recognized tobi as madara but what if it was surprise....like "you of all people" like the nine tails was shocked at who was controlling him? just a thought
Looking back at it, it seems like Kyuubi was saying something like "You...you bitch!". Seemed kinda pissed to me. A simple explanation like this is unlikely; just another option.
Kyuubi recognizing Hashirama's chakra is possible, though it would feel like an ass-pull, because the scene focused on the sharingan suggesting it's Madara. Don't know, doubt Kishi will even care to explain this panel.
Well, it's not weird that Kyuubi know who Obito is. The Bijuu sees everything from the Junchuriki eyes. So the question is if Kushina meet Obito at some point.
Obito being acquainted with Minato's wife? That seems fine to me.
BUT Kyuubi reaction looks like he is thinking "hey, isn't that the funny kid with googles?" for you? I don't think so, it is more like his typical "Madara, you motherfucket! I am gonna kill you!!"
And that masked guy said he waited for a long time for that occasion. So I wouldn't expect it to be Obito, or not that Kishimoto had it in mind.
Don't really know why people get hung up about that.
"you..." dosen't mean anything .....
"you.... who are you?"
"you.... how did you get in here?"
"you.... I can feel madaras presence in you..."
a thousand ways to finish this "sentence" without it clearly relating to madara....
I guess it could be explained as either Madara's presence somehow being in the Zetsu-suit (he is sleeping after all) or the "you" being misinterpreted.
Madara and Obito sharing the same body could also explain how Obito took on the Fourth...
...then again Uchiha teenagers with Mangekyo are usually overpowered.
Kishi is simply trying to emphasize what he said in the beginning:
"In this world, there exists kids younger than you, yet stronger than me."
"You...YOU!...Trollbito!!! DIE ALREADY!!!"
That's what Kyubi was trying to convey.