I've been pondering the whole time-space theory myself, and it's becoming clear time travel is more possible than not.
This is an article which explains time travel fairly well
http://www.bbc.co.uk/science/space/e...el/index.shtml
Take in consideration our whole concept of time is based upon the number of revolutions around the Sun. Time is, basicly, a relevance to where we are. Therefor, stepping out of this gravitational bound planet, we find there is no basis for time, and the very concept of time is mearly a perception.
Back to the topic...
The possibility of Jesus being an "alien" cannot be proved nor disproved. Simply put, we weren't there to witness his presence. What we have is the historical accounts written by man (humans) several thousands of years ago. The verbage used in the scripture makes reference to "the heavens" when speaking of what we know as "Heaven".
It is apparent "the heavens" mentioned in the scripture could possilbly be in reference to what we call "space". So, with this in mind, it is possible Jesus was from "space" or "the heavens" which would have us call him an alien. The word "alien" is defined, by Merriam-Webster Online Dictionary, as "differing in nature or character typically to the point of incompatibility."
With this definition I'd say that descibes Jesus to the T.