WATERSTON RETURN ROILS LAW & ORDER CAST

SAM WATERSTON’s return to Law & Order has thrown the set into chaos, with fellow stars Mariska Hargitay and Christopher Meloni irked because he’s acting like he’s king of the hill, say sources.

The 81-year-old Sam returned in his role as prosecutor Jack McCoy for the unprecedented three-hour crossover of Law & Order, Law & Order: SVU and Law & Order: Organized Crime and it turned into a huge headache for Mariska, 58, and Chris, 61.

He’s throwing his weight and opinions around, and Mariska and Chris are finding it hard to bite their tongues, sources dish.

“There’s lots of drama behind the scenes,” tattles an insider. “Shooting the crossover episode was torture for them.