I love discovering little hidden references in games, and during my time playing WoW, I've spotted a fair amount of in-jokes, from the various Goblins named after USS Enterprise crew members, to the Friday the 13th homage in Ellwyn Forest. The guys over at Blizzplanet, however, have done their homework far better than me. They've compiled an enormous list of easter eggs to be found throughout Azeroth, some of which I now realize that I had seen, but never made the connection before.
For example, the Psycho-themed names in the Undercity I should have gotten right away; I'm dissappointed in myself. And who'd have thought they'd squeeze in so many Thundercats references?