With Kirk Douglas in the news, this came to mind. Not to mention the trending story on Twitter that he may have violently raped Natalie Wood when she was 15 years old. I have no idea if there is any truth to this, but it might be worth digging into, along with the tunnels story.
"So, according this blueprint, tunnels were built to the homes of “Mr. J. Nicholson,” “Mr. W. Beatty,” “Mr. K. Douglas” and “Mr. J. Caan.” We’ll go ahead and assume they’re talking about Jack Nicholson, Warren Beatty, Kirk Douglas and James Caan – all of whom lived near the Playboy Mansion during the late 1970s and early 1980s. There are no dates on the architectural schematics, but the dates on the Polaroids were from 1977."
This was the only other document that referenced the tunnels.
https://www.playboy.com/read/tunnels-to-celebrity-homes-playboy-mansion