Steamboat Willie has been part of Disney animations trademark for at least a decade. It is literally the trademark animation used at the beginning of every Disney animation film.
And? Trademark isn't copyright law. It doesn't operate the same way. You can indicate that something isn't being used as a mark to indicate source (all trademark protects) and therefore it isn't necessarily an infringement of someone's mark, the same way direct verbatim copying would most likely be.
What's your point anyway? That copyright should be subsumed into trademark? Some others here are posting it, not that it makes any sense. Even funnier, they complain about the term limitations of copyright... but trademarks are indefinite.