Diesel and the Ducklings

S1, E6: Diesel likes to appear rough and tough but, when Thomas finds him lovingly fussing over some baby ducklings, he threatens to tell everyone that Diesel is really a big softie. Diesel is horrified and promises to be nice to everyone in exchange for Thomas not telling anyone. All the engines are pleasantly surprised when Diesel starts being polite and friendly, but just how long can he keep it up?