Think about it. He remembered the numbers only after hearing them once, He knew there was some sort of magnet, he knew the numbers flip BACK to 108. Desmond said that Kelvin/Calvin died, but where was he buried, and how did he die? I think Kelvin/Calvin went out to explore the island and left Desmond in the hatch. He met up with the others and decided to live the good life in another hatch(s).
Could be, if he was Kelvin and ventured out he could have been caught by the others and held against his will. I think there is more to Henry that him simply being a typical Other. This guy knows stuff, a lot more than he is letting on to.
I think he is more than Kelvin. His name alone (wizard of oz) indicated that he is bigger than that. Since his capture, what has happened to the other's happenings. It is because their leader is Henry.
Not-henry-gale seems much more sinister. i like the theory that he could be the return of Kelvin, but there is something more in his eyes and in his lies. i mean why would Kelvin go out of his way (and take a beating from hell) to lie soooo much to the losties. Kelvin was straight up with Desmond (a complete s tranger when they met) about the hatch, so why wouldnt he allow for similar admissions. perhaps he wants to find out more about the losties so he is being more covert, but who would take a beating like that for such odd reasoning. my take is that Kelvin is, as far as we have been told via Desmond, a straight shooter without too much to hide in regard to the hatch. this not-henry-gale guy is hiding all kinds of secrets...
What if this isn't the first time that fauxHenry has been in the hatch and lied about who he was. Maybe "Henry" was the one that found Desmond on the beach and fabricated a story about Kelvin. It's not like "Henry" isn't capable of fabricating a story about who he is. I think that there is some validity to him being more sinister than just Kelvin, but how do we know that Kelvin wasn't sinister. Desmond didn't give us a whole lot of info about Kelvin.
Can you explain how Kelvin was so straight up with Desmond about the hatch? My recollection tells me that Desmond let on that he knew very little about the hatch. Of course he could have been lying too. But, we never saw any interaction between Kelvin and Desmond, therefore there are no definitive statements that can be made about anything that happened betweent the two of them. I believe the "Henry" is going to turn out to be Kelvin. Whether or not Kelvin turns out to be someone else, maybe "Him", is another question.
Don't believe "Henry". He will Lie. He will Lie for a long time.
Maybe there is no Kelvin. Maybe Desmond is a plant by the others. It just seems like there are a whole lot of people who appear in flashbacks who end up on the island. Maybe all these appearances are not just coincidences. Just a random thought.