I am planning to register my finished product electronically in the copyright office.

I have a screenplay, a website and an animated short movie made from poser.

I think I can only copyright the screenplay which contain the story and the character names.

The website name, I am not sure.

The renders, I am thinking not because they are from poser figures and props and they might change in the future.

If I decide to make small episodes based from the original story in the future, do I have to copyright each screenplay?

Passion is anger and love combined. So if it looks angry, give it some love!