Candace Loses Her Head - S1-E7
Continuity mistake: At the starting of the episode when Phineas wakes up you can see right next to him there are two pillows on his bed but when he sees the calendar and is about to throw the pillow on Ferb you can see that there is only one pillow.
Answer: "One boring day, Phineas recognizes an important truth; Summer vacation will end, and the teachers will want to know what they did on their summer vacation. And with these two kids, it has to be something extravagant..."http://uk.imdb.com/title/tt0852863/.
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