The Creature template has the following features

It automatically adds the page to the Creature category, as well as appropriate race and type categories if the Type parameter is fed a link (if you feed it a single word it will be unpredictable) and adds it to Unique and Melee if appropriate.

If you type a single word into the parameter TypeLink it will transform it into a link to the category page of that type. Don't use it with the Type parameter