I was thinking maybe it's not aliens in the "classic" sense, but creatures that reside in other dimensions that created our whole universe as a science project. And these creatures (whom we can, by definition, never possibly hope to come into contact with ...ever) create "time" as a property and limit of our universe. Consider our universe a marble. This marble is represented in three dimensions, like a normal marble, but one of those dimensions is time. One two dimensional slice of the marble would represent one three dimensional state of the universe in a point in time. To the creators, the marble would be spherical, all points in time existing at once, without our perception of change and linearity, but we are forced to travel along the dimension of time in one direction.
So at one arbitrary end of the marble, time starts (Big Bang: why not?), and at the other end, time ends. In between is X amount of our "years". Time, as we know it, would not affect these creatures, and unfortunately, since they live in dimensions outside our universe, we can never contact, or even begin to comprehend them. If you want to take into account quantum multiverse ...stuff, then I guess you'd add another dimension to the marble, so one two dimensional slice of the marble would represent every possible history of that universe at that one point in time.
Tell me if this makes any amount of sense, in any way. It's something I thought up late one night trying to get to sleep. /ttiforum/images/graemlins/frown.gif
...but within that frame, I guess it is possible that some "sentient" species decided to stick some life on a suitable planet to see what happened, and BAM, some millenia later, here we are, chatting on a forum about the possibility of that exact thing happening. ...It's possible.
Oh, welcome!