I have been suggesting that its Michael affecting the world trough a short of CHIM but there is also the possibility that this is all illusions.
I find it interesting that the more we believed it to be the mane six the more strongly they became so, Applejack is nearly caricature while our earlier encounters are more unclear. Tough this may be due to writer frustration (I wonder, since we can communicate with Michael, maybe the writer is also an active part, so to speak?).
Of course, this may still be the CHIM effect, but I think it being illusions from a third partner explains some things. Well, I think its likely illusions what with the tentacle thing.
Whats more, its possible that these are illusions by somebody who do not know what they are making illusions of. That is, this is a form of illusion spell that lets the person under spell subconsciously fit in the details of what they see and perhaps partly what they hear too. So whatever behind the illusion does not really know what the hell Applejack is and thus is surprised by the name and thus also ask us to elaborate and vocalize what we are thinking. They can obfuscate the looks and manner of speech but they don't have the knowledge said entity should have. It may also explain how you feel hunger without hunger existing in the world since the spells lets you fit in the necessary details yourself.
Obviously we got someone with an interest in you who really wants you to eat the apple for whatever reason. What that reason is we don't know. It may be a trap, it may be a way to contact you secretly, it may be something else entirely. We don't know who the entity is, tough the tentacle thing does hint towards ascended sleepers (and Dagoth Ur have been know to play around with dreams, what this might be), and thus we don't know if the apple is for good or ill.
I am interested in eating the apple simply to see what happens, its likely that something interesting and informative may happen unless its simply death. Curiousity killed the cat, eh? Examine the apple with your magic eye. Show it to someone else. Possibly eat it, if they wanted to kill you or capture you they where close enough to do it before anyway.
Amusingly, this situation is also possibly a short of a biblical parallel Adam (a man, Michael) gets an apple (a woman, Applejack) that bestow knowledge of life and death/god and evil (for the curious).