Morphing
From CGAFaq
Morphing is the name that has come to be applied to the technique ILM used in the movie "Willow", where one object changes into another by changing both its shape and picture detail. It was a 2D image manipulation, and has been done in different ways. The first method published was by Thad Beier at PDI. Michael Jackson famously used morphing in his music videos, notably "Black or White". The word is now used more generally.
For more, see [Anderson], Chapter 3, pp. 59–90, and Beier’s
Link to Heckberts morph videos
