I’m not totally sure if you could make a sequel under trade mark law since the Mickey character is still trade marked for new works, maybe if it were free it would be ok. If you wanted to use clips from the original work in a music video or something then you should be able to do that.
Trademark law only prohibits the use of a trademarked character if doing so “is likely to cause confusion, or to cause mistake, or to deceive” consumers about the source or sponsorship of the new product
I’m not totally sure if you could make a sequel under trade mark law since the Mickey character is still trade marked for new works, maybe if it were free it would be ok. If you wanted to use clips from the original work in a music video or something then you should be able to do that.
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https://web.law.duke.edu/cspd/mickey/