The guidelines to follow about what elements are worthy of a whole page on Scrooge McDuck Wikis, and which are not. Keep in mind that those are only general guidelines and not strict rules.
Characters who have a great importance within the story, or have some ties to the main characters (such as family ties) or to their history, are priority. However, ideally, all named characters appearing in a story that has a page on the wiki should also have pages of their own. Nameless characters should only be given pages if they are of special notability (either through their importance in the plot or through an unusual concept).
All stories, no matter how short or obscure, are theoretically worthy of a page. The exception to this would be foreign stories that have not yet been translated in English; of those, only the more notable ones (like the first appearance of a recurring character) ought to receive pages. (The point is, no one's going to come after you to delete it if you create a page about a random 1986 Italian one-shot… but stories available in English should be a priority for editors.)