* Counting methods: Do we count movies, TV shows, shorts, documentaries?
* Data availability: Accurate data on film appearances isn't always publicly accessible.
* Definition of "film": Do we include voice acting or uncredited appearances?
That being said, some of the actors frequently cited as having appeared in the most films include:
* Christopher Lee: He's often mentioned as having a prolific career, with estimates ranging from hundreds to over 250 films.
* Donald Pleasence: Another actor with a long career, his filmography is also quite extensive.
* Eric Roberts: Known for his diverse roles, Roberts has an impressive list of appearances.
Note: These are just a few examples, and there are many other actors with incredibly long and varied careers.
To find a more definitive answer, you could consult resources like the Internet Movie Database (IMDb) or other film databases. However, keep in mind that even these sources might have differing data and counting methods.