Tosh is a walking Doomed Romance - poor girl never gets a break! It's like the writers couldn't come up with anything else to do with her! Sad when you consider what an inspiring character she could have been with a bit more effort on the part of the writers. All their effort seemed to go into exploring Gwen and Gwen's Life and Gwen's Relationships, and for all that, they failed to make her anything more than dull and boring - for me, anyway. Gwen was nothing I hadn't seen before, just written worse andmade less likeable. I found the snippets of Tosh's life much more interesting. I may not be a brain like Tosh, but I'm geeky and quiet and I've been overlooked or ignored most of my life, so I found her (and Ianto) much easier to identify with, and much more interesting as multi-layered characters.

An essay could be interesting, plus it would give you a good excuse to watch everything again in order to check your facts and look for any other examples ;)