Masking or whatever?

as far as i know this may not be possible using masking, but i’ve searched kirupa and google and have not found what i’m looking for, so i’m gonna ask.

1st question…

is it possible to make an image slide into view out of thin air? (keep in mind that the image is not a layered image)

example1: say you have a picture of a blue sky (no clouds). how would you make a picture of a mans head suddenly slide into view out of thin air?
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example2:** say you have a picture of a field with one tree standing in the middle of the field. you also have a picture of a horse (but you cannot see the horse yet). how would you make the horse slide out from behind the tree making it seem like the horse is appearing out of nowhere from behind the tree, even though the horse is much wider than the tree?

2nd question…

how do you do this using flash?

thanks,

opusmx