[daleswanson]

See for example, the Star Trek TNG episode that used Sherlock Holmes. At the time, the studio assumed Sherlock Holmes was in the public domain, but were contacted by the estate and told they would have to license the character if they wanted to use him again. This almost prevented a follow up episode, and probably did prevent other follow ups to what was considered a good story line.

http://en.memory-alpha.org/wiki/Elementary,_Dear_Data