Posterwire explains the arcane picture approval process for movie posters, which can lead to an actor’s approved head-shot being grafted onto several different bodies.
Using the same head on different bodies isn’t uncommon (and sometimes a necessary evil).
[…] Most well-known movie stars have approval (either contractually or as a
professional courtesy) over ALL photography of themselves available to
a film’s marketing campaign. For example, when images from a film (in
unit shots, special shoots, etc.) become available, the images are first given to the actor for approval. Contact sheets (also known as proof sheets)
of all the photography are sent to the actor, which are then sent back
with a lot of red Xs — known as "kills" — marked through photos that
the star (or more likely, their manager) don’t want used. This can be
frustrating for designers working on the project if some/most/all of
the best shots are "killed". This power to "kill" can be taken a step
further when a star (or producer, director, etc.) has approval over the
movie poster design of the final one-sheet. This is why one of the
first questions asked by many art directors on many key art projects
is: "Who has approval over this movie poster?"
What I don’t get is why they sometimes airbrush the actor’s face to the point that they barely resemble themselves. Take, for instance, the picture on the left of Tony Shalhoub (click on the picture for a larger image) from one of the Monk DVD sets. What have they done to his face??