Marvel successfully argued that the characters from X-Men are not humans to dodge paying higher taxes.

This takes a bit of explaining. If you’re well immersed in the world of X-Men, it might sound strange to you that Marvel claims the mutants aren’t human. In the source material, mutants are treated to the reader as very human. 

Well it’s all because of a strange law on imported goods. There is a law in the United States that basically raises taxes on imported goods (specifically toys) that resemble humans. 

Marvel action figures (like the X-Men) are generally made in other countries and are then imported. Because they all resemble humans, Marvel would have to pay much more in taxes under the current trade laws. 

Marvel managed to argue in court, though, that the X-Men, as well as Spiderman and the Fantastic Four resemble animals or non human creatures, and so the toys should be exempt from the higher tax. That's kind of ironic, since one of the biggest points of the X-Men series has always been about the struggle of the X-Men to be recognized as humans by the rest of society!