Development teams play a bit of Calvinball whenever they purport to follow an Agile methodology like Scrum. Why? Because of the fourth principle of the Agile Manifesto: responding to change over following a plan. If you’re planning to follow Scrum, then that’s your plan. But to follow Scrum, you need to be willing to throw out the plan. In other words, you get to make up new rules as you go along. Calvinball!
Read the entire post at http://blog.devx.com/2012/07/the-scrum-but-paradox.html