There’s been this thing spreading round base that long haired tobi and short haired tobi must be different people because of events and height issues but let me tell you now, the mask men have always been the same people. I know this because I realised the differences such as height and events about last year, but every time I make a theory I try and prove my theory wrong and see if it can hold.
What people need to remember is that the first time we ever see Tobi he has short hair and this was the Kyuubi incident. Itachi was 5/6 when this happened (I have done all the calculations to work out age).
Theory: Sometime after the kyuubi incident maybe the same year Tobi went to the village hidden in the mist to whatever deeds needed to be done there. For whatever reason he let his hair grow maybe he was to busy controlling the mizukage maybe he wanted a new identity who knows why read on.
When Tobi revealed himself to Kisiame this is years after the Kyuubi incident it is around when Itachi was 13. So the Tobi having long hair at this point is possible because this is 8 years after the kyuubi incident.
The reason itachi looked so short compared to this long haired Tobi is because Itachi is only 13(makes sense now don’t it), the itachi we see today is 21/22. So the itachi here is probably like sasuke’s height when sasuke was 13 which is why Tobi with long hair looks so much taller than him.
Theory: Tobi has been controlling the mizukage for years now people may have been on to him because of this he needed a new identity so he changed his mask, his hairand also his voice. Now you may think this is stupid and how the hell would anyone fall for this, but what you have to remember is:
1) This is a Manga 2) Loads of ninja’s wear masks (haku, anbu..) and 3) it worked! Kisame thought tobi was a new member of akustki and itachi thought this as well. That is why Tobi had to re-reveal himself to kisame again because his disguised had paid off people didn’t know he was the mask man from the past.
Now everything I just said is enough to prove he is the same mask man but I will give you one more reason which I could of used to prove he was the same masked man single handily but I like to make long threads that go into full detail to create good reads. Anyway the last reason is that the voice used of serious short haired Tobi and long haired Tobi is the same. (":sy::sy::sy: How could I ever think they were different people" is what your thinking now isn't it)
This also could of been used to prove that Tobi was not Madara a long time ago because in the NUNS: Generations video they took away madara’s voice, why? Because his real voice has not been revealed yet and will be revealed in the anime shortly. This is why all the other characters voices was there and done by the voice actors but Madara’s ws not.