system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we say someone was "in" a movie, but "on" a TV show?
gpt
It's an interesting phenomenon that goes back to how television was first referred to. A television is a physical object, so when you watched one, you were watching the pictures projected *on* the television screen. "Look, the president is *on* the television." 

A movie, however, is not perceived as a physical object, but is instead a collection of information, much like a book or song. Someone is in a movie in that they are included in the collection of information the movie contains 

Over time these definitions have merged and blurred, but we still have the "in vs on" division as a relic of an older style of language.