There are numerous pages for shows that i am a geek of, which to me appear to be rather anemic as far as tropes listed as concerned.
Is it OK to input a large number of tropes into an existing page or is it normally left to whoever created the page in the first place?
This Is A Wiki. Anyone can edit it, as long as you follow the guidelines. Nobody owns an article and if you find one that needs to be fleshed out, we highly encourage you to do so. This is what we call Wiki Magic. In short, please do that!