Taken in isolation, two clips should rarely be used to 'prove' anything. As such, we should preface this by saying that McGregor could be doing a number of things here but when you put this dressing room footage beside the 13 second fight footage, it's incredibly compelling to watch.
Quite a while before he stepped out for the main event of the evening, the dressing room camera caught McGregor engaging in a little bit of practice. There's nothing particularly noteworthy about a bit of shadow boxing in the build up to a fight.
On it's own, McGregor's dressing room practice is intriguing to watch, but when a reddit user by the name of Bibosas put it alongside the fight footage, it's almost mesmerising. A mocking of Aldo's head forward stance, a quick dodge of an imaginary punch and a powerful left hand. That Mystic Mac nickname is not going anywhere any time soon.
See also: The 13 Dejected, Defeated Minutes Jose Aldo Spent Facing The Dressing Room Wall
Here it is with sound just in case that makes it even better.
Given that this was from before Gunnar Nelson's fight, another explanation could be that he was giving Gunni some tips on how to deal with Demian Maia. However, that was always going to be a grappling masterclass so we're not sure how much use that advice would have been.
Nonetheless, even if it was some advice as opposed to some practice for McGregor himself, it's an incredible coincidence to what extent that small bit of shadow boxing played out in real life when it really came down to it a couple of hours later.
See also: Joe Rogan Apologises For Confusion Caused By Jose Aldo Post-Fight Interview
GIF via /r/mma