This is interesting. I opposed the Mickey Mouse Protection Act of 1998 (officially the Copyright Term Extension Act), sponsored by Sonny Bono (R-CA), because I (a) believe that copyright protection already went on too long (50 to 70 years), and (b) it was such a naked lobbying bid by Disney.
Well, it turns out, Disney's copyright in the Mickey Mouse character may actually have lapsed in 1998 despite the Act:
Film credits from the 1920s revealed imprecision in copyright claims that some experts say could invalidate Disney's long-held copyright, though a Disney lawyer dismissed that idea as "frivolous."
Today, title-card claims are no longer required. But when courts rule on historical copyright issues, they follow the laws in place at the time—in this case, says [Georgetown University law graduate Douglas] Hedenkamp, the 1909 law requiring that the word copyright or its symbol be "accompanied by the name of the copyright proprietor"—a rule scholars said means in the immediate proximity.
The article isn't exactly law-journal ready, but it gives a reasonable outline of the issues. I'm not expecting anyone to challenge Disney on this, but it's funny to me how they spend a lot of time yelling and screaming to protect their Mickey Mouse trademark even when they know they've lost the copyright on several films, and possibly the character itself.