Henry the Green Engine (The Railway Series, seasons 1-11, 17, 20-24)

Henry The Green Engine is a fictional mixed-traffic engine in the British Railway Series books by Wilbert Awdry and his son, Christopher, published from 1945. He is one of the first engines to appear in the franchise with Edward The Blue Engine (who was the first) and Gordon The Big Engine. He also accompanied Thomas and other characters in the television adaptation series Thomas & Friends (aka Thomas the Tank Engine or Thomas the Tank Engine & Friends). According to The Unlucky Tug, he has appeared in more books than Thomas himself.