User blog comment:AgentGoldfish/Comic-Con Questions for Dan and Swampy/@comment-2133790-20100720204459

Well, some episodes never actually happened. Like Phineas and Ferb get Busted. Then in ones like She's the Mayor, where everything was reversed, Phineas and Ferb might have come up with a different idea and that turned into a different episode. And you never know, two episodes may have actually happened in one day.