S2·E39 Percy in the Middle

After Gordon tells all the young engines that they have a day off to relax, Thomas and Diesel insist on a teamed relay race through the obstacle course. Percy is the only one who isn't interested in playing, so Thomas asks him to referee instead. He reluctantly agrees and the race is on! Coming to a split-second finish, Percy determines Thomas' team wins, but Diesel doesn't accept and calls for a rematch. Once again the teams race and Diesel wins after accidentally causing an oil spill. Both teams become so angry with each other, they're too distracted when Percy runs off to chase butterflies. Thomas, Diesel, and friends finally notice Percy's absence and speed after him, but they'll need to learn their lesson about sportsmanship if they want to ensure this day off is a success.