This drawing shows a tunnel running underneath the Playboy Mansion to the "residence of Mr J. Nicholson." It's one of a couple blueprints found in the unfinished basement of the Mansion in Holmby Hills that also shows underground tunnels to the homes of "Mr. W. Beatty," "Mr. J. Caan," and "Mr. K. Douglas." Warren Beatty, James Caan, Kirk Douglas, and Jack Nicholson were all in the neighborhood in the late 1970s and early 1980s, which is the approximate time that these passageways are said to have existed—if they existed at all, says Playboy (via BLDG Blog).