This is an in-universe category. Please do not place any story categories, like category:Sarah Jane Smith stories, here.
Please also do not place this category within very specific categories, as this creates recursion in the category tree. It's also not true, because when you put the category SJS into , then you actually put Clyde, Rani, Luke, the Bane, the Slitheen, sonic lipstick, 13 Bannerman Road, and tons of other SJS-related stuff into that category too.
Like category:The Doctor, this category belongs only in a very top-level category, so as to reduce recursion. As of March 2012, it's been placed in category:Time-Space Visualiser, the top-most in-universe category. Meanwhile the page Sarah Jane Smith gets put into various subcategories, like category:Fourth Doctor companions, category:human journalists and the like.