Some of the staff on OK K.O.! Let's Be Heroes aren't a proper part of the crew. Rather, they're freelancers who generally work on a few episodes, often having a full time job on a different show at the same time, or in between full time jobs. Sometimes a freelancer ends up getting a full time job on the show later on, which is why some full time crew members are also in this category, as they started out as freelancers.