What was changed in the original script? *spoilers*

The original script was called "The Cellar" and was supposed to be a micro-budget film about a group of people trapped in one location, until JJ Abrams apparently saw it fit to change some parts to make it fit into the Cloverfield universe. What did he change or add? Did the script originally include aliens? I hated the sudden inclusion of aliens at the end and would have preferred an earth-borne threat.