I had to look it up:
It turns out there was a reason why Caruso behaved so badly on the set of NYPD Blue. According to Steven Bochco, it was because he wanted to be removed from the show. In his memoir, the producer writes:
"He never said it to me directly, but the simple truth was, Caruso felt he was too good for television...He wanted to be a movie star. And his plan was to alienate the writers, producers, and his fellow castmates in hopes that we would dump him from the show.”
Towards the end of the first season of the show, Caruso asked to be relieved of his contractual obligations, but the show's producers refused to let him leave. They didn't want to jeopardize the future of NYPD Blue because, after one season, the show had become a breakaway hit.
It was at this point that things became more difficult. When working on the second series scripts, Caruso's agent got in touch with the producers to let them know about the actor's new demands. If he wasn't to be let out of his contract, he wanted it to be restructured.
Under a new deal, Caruso wanted a pay rise from $40,000 to $100,000 per episode. He also wanted Fridays off, a 38-foot trailer, his own office suite, a dozen first-class plane tickets, and private security to protect him from his fans. The agent informed Bochco that, if these demands weren't accepted, the actor had another series of demands, which included time off the show so he could concentrate on his movie work.
Understandably, Bochco rejected Caruso's demands and even threatened to sue the actor if he didn't return for season 2. But as things became more difficult between the actor and the program's showrunners, push eventually came to shove. After many other battles with the actor, they agreed to the termination of Caruso's contract to let him pursue his hoped-for film career. Their final stipulation was for him to do the first four episodes of season 2 so they could properly write him out of the show. Caruso agreed, although his behavior was still less than warm on the final day of his time on the show. Bochco said in his memoir:
"When he had shot his last scene of the fourth episode, he turned without a word and left the set, the stage and the lot. He didn't say a single word of thanks or a goodbye to his castmates — nothing."
So yeah, he was a NTP66.