SFU Education PhD student Deanna Peluso has just written a funny 2-part piece on her blog, comparing graduate school to World of Warcraft. (Part 1 | Part 2)
World of Warcraft: Choosing your character class (e.g. Warrior, Paladin, Rogue, Mage) affects the types of things you can do in-game and what talents you can hone. It is based on the faction (Alliance or Horde) that you originally chose. While changing your faction is possible, it is costly (money) and really, just make up your mind ahead of time.
Graduate School: Choosing the specialization for your degree affects the types of courses you will take, and ultimately the types of knowledge and skills you will gain from your degree. While changing your specialization after the fact is possible, it is costly (wastes time in your graduate studies) and again, really, just do your research ahead of time, or take a directed/independent readings/studies course if you really wanted to study that topic that isn’t offered as a regular class.