"Billy Goat Gruff" is a popular Norwegian fairy tale about three billy goats who want to cross a bridge to reach a meadow full of grass. The bridge is guarded by a fearsome troll who threatens to eat anyone who tries to cross. The story follows the three goats as they cleverly outsmart the troll, each one crossing the bridge in turn. The tale emphasizes themes of bravery and cleverness. The smallest goat tricks the troll into thinking that the largest goat is much bigger and stronger, leading to the troll's downfall. This story is often used to teach children about problem-solving and the importance of teamwork.