Protections over copyrighted works, especially those related to images and characters, can live on through derivative works and trademarks even after the original work’s copyright has expired. Therefore, producers of creative works should prepare for the expiration of their own works and take caution when borrowing from works already in the public domain.

Copyrights are a constitutionally created protection over original works of authorship for a limited time. But when a copyright protecting a first work in a series expires and the work enters the public domain, the later works in the series (known as derivative works) maintain separate copyright protections. These protections are limited to the elements original to the derivative work; as a character develops throughout a series, the polished, idiosyncratic, and possibly more well-known final portrayal of that character can maintain protection after the rough, less-refined elements of the character fall into the public domain.

Copyright protection may be supplemented by trademark-able elements of a copyrighted work. Images, quips, soundbites, and other recognizable elements from a work can be incorporated into logos, marketing campaigns, and other products as trademarks. Because trademark rights are lost only due to a lack of use, trademarking recognizable elements from a copyrighted work can protect some of the most important elements of the work from undesired public use indefinitely, even after copyright protection for that work expires.

For example, 2023 marks the final year of copyright protection for the original Mickey Mouse cartoon, Steamboat Willie. But even though the eight-minute animation will fall into the public domain, Disney has taken steps to maintain rights over its beloved mouse mascot. Over the years, Mickey Mouse has been transformed from a rambunctious, animalistic form into the softer, familial, colorful character known today. More recently, Walt Disney Animation Studios inserted Mickey’s original form into a trademark protected logo and continues to sell Steamboat Willie merchandise. By taking these steps, Disney will be able to continue policing public use of their flagship mascot.

Accordingly, it is crucial not only to prepare for the eventual expiration of a copyright, but also to fully assess using unoriginal works from the public domain because the underlying work may be protected under other areas of the law.