1x13 - The Melancholy of Haruhi Suzumiya

Haruhi takes the SOS Brigade on a whirlwind tour of summer activities almost identical to the previous episode. Kyon is wracked by déjà vu, and when Mikuru finds she can't return to the future, Itsuki figures out that Haruhi has put the last two weeks of August into an infinite loop. Yuki reports that the loop has repeated 15,498 times, though with variations on individual events. At their meeting in a restaurant on August 30, Kyon realizes the truth in Itsuki's theory that Haruhi is repeating summer vacation because there is one more thing she hopes to do. He fails to think of anything he can do to satisfy her, and resigns to the loop continuing.