There's a great story along these lines about Star Trek. At one point, Paramount's legal team fell asleep at the wheel, and the first dozen or 15 episodes of the original series slipped into the public domain. A fly-by-night video company contacted to Paramount to inform them of their intention to release these episodes on video.
Paramount responded, and I'm paraphrasing, as follows: "OK. You can't use the name Star Trek, which is trademarked. You can't show any interior or exterior shots of the Enterprise, which is under separate copyright. You can't use the theme music, which is under copyright. And you can't use any scenes scored with music, all of which is under copyright. If you can edit together coherent shows that avoid all of the above, be our guest."
Needless to say, the PD releases didn't happen.