To add a new category to a page you can click the Category button at the bottom of the page and type in the name you'd like your category to be called.
A full list of existing categories can be found at Special:Categories.
Pages in category "Browse"
“ A list of characters who either were mentioned or made no appearance to any episodes at all.
“ Pages in this category have been labelled for deletion. To add a page to this category, type...
Candidates for deletion
“ This category contains disambiguation pages — navigational aids which list other pages that...
“ This page lists a number of actors of any type who had either once participated in the series...