"Creation Requires Influence" is the quote that justifies this. Its pretty much impossible to creative something without any form of "copying" modifying or sampling. Even todays most successful artists, designers, entrepreneurs, engineers, inventors, etc have been guilty of doing this at least one if not throughout their whole career. There is a huge difference between influence, and straight up copying someone else's work and calling it our own.
Based on this, there are two "remixes" that come to my mind.
First is the popular Nicki Minaj song "anaconda" which uses a samples of "Baby Got Back" throughout the whole song. Minaj rapes her verses, while the sample music is used as a template:
Another example of a "remix", which I personally thing is a straight out theft of art work is Jeff Koons's "Dr. Dunkenstein" from his series "Equilibrium", a Nike poster from the 1970s of former Utah Jazz player Darrel Griffith. This poster came from another artist who came up with, and photographed the concept for the poster. All Koons did was frame it and called it his art. Unfortunately I have not found the original artist for the Nike Campaign.
Copyright laws have both pros and cons. While the intention of these laws are to protect the works of these creators, a lot tend to be extremely vague and therefore easier to sue and get money from basically anyone. They breach the nature of the internet and its foundations, like fanwork, which is a giant culture of the online world. Anyone who creates fan art or fan fiction can easily be sued. Same goes to basically anything with any amount of copyrighted images, songs, even mentions.