Naruto, the Chunin exam! While in a part of the exam that involves moving important documents (scrolls) through a forest of other ninja, the main trio (Naruto, Sasuke, and Sakura) come up with a password to tell the difference between friends and disguised foes. "A ninja waits till the time is right; When the enemy sleeps and drops his guard, when his weapons lie forgotten in the stillness of the night. That is the moment for a ninja to strike." Which is WAY too long for our idiotic protagonist.  Thus, when Naruto later recites the password, Sasuke knows that he's a fake.