How does copyright law apply to references of an existing work?
<p>If an author were to reference an existing work of fiction in their novel, how does that interact with copyright law?</p>
<p>For instance, let's say a character in a novel thinks they're a fictional character, like Joker. In the universe of this novel, DC exists, and Joker is a known fictional character. No one in universe would take this character seriously as the Joker - he would more likely be considered to be delusional, and possibly dangerous.</p>
<p>Would something like this be legal to release? Would it require special provisions and/or disclaimers?</p>

<p>Literary references are generally considered to be a form of Fair Use in the US, and a form of Fair Dealing in those countries that have that legal concept. Mentioning that a character has read a fictional work, or likes a character in na fictional work, or even models his actions on such a character, or thinks he is that character is not treated as an infringement of copyright.</p>
<p>Indeed, even &quot;cameo&quot; appearances of a literary character are not usually treated as infringements. A character in a period mystery might briefly meet Sherlock Holmes or Hercule Poirot, say, without that being an infringement.</p>
<p>If significant sections of the new work involve imitating the plot of the source work, while the delusional character tries to act out his or her delusion, that <strong>might</strong> make the work a <em>derivative work</em> of the source (here DC comics). Creating a derivative work requires permission from the copyright holder.</p>
<p>Whether a work is derivative depends on the specific facts, and cannot be judged from the information in the  question. The more of the specific details from the source work that are used, and the more extensive the use is within the new work, the more likely it is that the new work would be held to be derivative. The details will matter, and ultimately it would be a matter for the judgement of a court if a suit were brought claiming that the work was derivative.</p>

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