Back at the Barnyard (2007)

Season 2: Episode 6

The animals turn the barnyard into a Wild West theme park to raise the Farmer's bail money (who got arrested because of Otis wearing a viking helmet and mooning a cop) and decide to hire an actor to play the bandit. Instead of an actor, unfortunately, a real bandit shows up to pillage the town. So Pig comes to Otis' rescue with unicorns from the unicorn theme park to stop the bandit from attacking the barnyard.