All categories on the Joepedia: The G.I. Joe Wikia should be reachable by browsing the list of categories that starts with this, "top-level" category. In principle, every article should be in at least one category, and every category should be a subcategory of at least one other. This means that every article on the wiki, ideally, can be found either by using the search box or by browsing the category structure.
If you find a category that is not accessible through this list, please add it to the hierarchy. You can add a category to another category (making it a subcategory) just like with any other page: edit the page, and add [[Category:Some category]] to the bottom.
This category has the following 20 subcategories, out of 20 total.