MorphX: the freeware for morphing in Mac OS X – Macitynet.it
It is a software born on Nexstep that allows you to calculate videos with transitions that transform one object into another: it allows you to manage groups of images and is completely free. In just 85k of code it will allow you to transform sheep into lions, thin in fat, young in old and in any case make nice caricatures by creating a sort of continuous mix between two faces. It will not be easy to use it for professional special effects (it is limited to images with 8 bits per color) but it will certainly be able to represent one extra creative tool and fun.
You can download Morph X from this page which also contains examples and source code to be used also within future graphic applications.