Back at the Barnyard (2007)

Season 2: Episode 44

The leprechaun steals the farmer's potatoes after Otis sprayed the potatoes, Otis and pals must stop him before the farmer goes bankrupt and the animals for less outlet. Unfortunately, also, the leprechaun turns Freddy and Peck into shamrocks and Pig into a corn beef sandwich head. Luckily, Otis gets an idea to cut out the middle man meaning to find the leprechaun's gold instead of catching him to surrender.