A combination of blue / green screen, After Effects and masks I
suspect. Time for deep pockets and lots of time....

Haven't used After Effects - I'm close to buying ULead Mediastudio Pro 7
after trying out the demo version (can get it at a good price, thanks to
the
upgrade path). I think it does masks and things, but I haven't looked at
any
of that yet. The full version also comes with something called Video
Paint,
which I gather is some sort of retouching package. It does sound awfully
tedious, though.

MSP's abilities with blue/greenscreen are a source of annoyance for a lot of
regular users. The lower-end Ulead products are beginning to acquire the
feature, while the upper end have been neglected for some time (apparently
so - I don't have much need for compositing).

If you can get hold of an earlier version (there was a fully legit version
of it on the cover of a January magazine - sorry can't remember which one)
then you can make use of some of the free compositing filters offered at
jushhome.com, which improve on the abilities of Ulead's own overlay filters,
but (unfortunately) they have yet to be compiled for version 7.