North Korean illustrators and graphic designers appear to have helped produce work for US animation studios unbeknownst to those companies, suggesting that unreleased episodes of a few popular American cartoons could include work from one of the most closed-off economies in the world.
It's been this way for a long time. SEK Studio, North Korea's production company, worked on The Simpsons Movie, Futurama and Avatar: The Last Airbender. (They did not work on Disney films, that's just a rumor.)