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.
My guess would be they went with a low bidder South Korean contract who then immediately farmed it out to North Korea and didn’t tell anyone.
This is mist likely what happened. A lot of animation gets done in South Korea.
FTFY.
That sounds likely as well.