Film Twins

Basically films that were conceived in some way from another production and cannot exist without the original.
Inspired by: https://henridecorinth.wordpress.com/2016/03/22/on-portabellas-cuadecuc-vampir/

Examples include:
1) A film compiled together using the original’s outtakes.
2) Behind-the-scenes footage compiled together to make a film. BtS documentaries alone don’t qualify unless they’re doing something different with the material.
3) A separate film that was made using the original’s budget (i.e. two films for the price of one).
4) Re-edit of the original to form something...