This may be completely wrong, and will expose my complete ignorance of modern popular phraseology, but...
Are you sure the phrase was "early screamer" and not "early screener", or "early screening"?
If it was "early screener", then it might mean a film or an actor/actress from the early days of film-making. If it was an "early screening", then it was a showing of a film - either just after it had been released, or else early in the cinema programme for that evening.
[Waits for ridicule....]
PS: It should be "What does this phrase mean?"