Well any show that lasts 11 seasons obviously has a pretty large fan base already, especially from the same crowd that plays games online.
Is it just me or is it that Gamers love Cartoons. I am not sure if there is a true correlation there or not, but seems to hold true with all the gamers I know.
But to say that one episode brought in a lot of fans, I'm not to sure, maybe a few, but I think most were already watching, and just happy to see a WOW episode.