You may remember Hey Arnold for Stoop Kid, Helga's unrequited love, or, of course, the main character's unforgettable football head. You laughed along as the gang navigated the sticky situations that come up in middle school. But you probably didn't catch all of the adult jokes in the show. Maybe you noticed your parents giggling mysteriously at certain moments while you obliviously smiled along with Harold or Grandpa. Well, they were probably laughing at one of the many dirty jokes in the cartoon. Check out these list of adult jokes in Hey Arnold to find out what you were missing the whole time. You'll never look at cartoons the same way again.