The Vulture (1967) - IMDb

Eric arrives as the Professor's home, where he finds a nuclear-powered laboratory in the basement. A skeleton sits at a control panel, and a small broken casket of gold coins lies on a nearby counter. It seems the Professor, speculating on whether or not he might have been related to the entombed man, and looking for the gold, had used his equipment to momentarily exchange himself for the contents of the buried coffin

Not such a good idea. The swap hadn't reversed itself, and his atoms had mixed with the remains of the bird. The composite creature had then broken out of the grave