When Scrat's acorn sends an asteroid to Earth, the Herd must find a way to stop the asteroid from hitting Earth with the help of a returning friend.When Scrat's acorn sends an asteroid to Earth, the Herd must find a way to stop the asteroid from hitting Earth with the help of a returning friend.When Scrat's acorn sends an asteroid to Earth, the Herd must find a way to stop the asteroid from hitting Earth with the help of a returning friend.