Im just wondering whether theres a movie editing software, where you have and original movie e.g starwars, and then you can put someone elses head on one of the characters, and change it frame by frame.

A bit like adobe image ready, but for videos.

its not an easy thing to do, but adobe after effects will.
your going to have to practice to make somthing decent tho

thanks.

you could also use discreet combustion, which can track specific pixels whether it be a head or a skin blemish which can then be seemlessly covered by other footage of your choosing, they use the software in films like master and comander aswell as tv shows like mutant x, it's extremly powerful and has a 30day trial on the site. hope this helps.