Tom Cruise and Katie Holmes' divorce comes down to one thing -- Scientology ... and Katie's fears about Suri getting more involved in it. We'll explain when and why things took a turn for the worse in the Cruise household. Plus, Mel Gibson's accused of losing his cool -- again ... this time with his 78-year-old stepmom. Even by Mel standards this is a crazy lawsuit. Also, Brad Pitt's brother gets his turn in the spotlight ... it's hysterical -- and a new addition to the TMZ Live fam joins Harv!