When Thomas travelled to China, he met Yen. She told Thomas about the Chinese New Year celebrations, and informed him how the calendar on Sodor was different to that of China. Later, Yen told Thomas he was very lucky as he had a paper dragon amongst his passengers. Thomas was frightened at first, but she assured him that the dragon was a symbol of good luck.
Yen is based on the narrow gauge C2 Class 0-8-0, which were used on various Chinese industrial railways and modelled after earlier designs built in Poland and Russia. Members of this class were in service until well into the 2000s. A member of this class, Dahuichang 4, has been preserved by the Ffestiniog Railway.
Yen is painted red with black lining and a black tender
- Yen has several modifications from her basis:
- She has been regauged from narrow gauge to standard gauge.
- Her first six wheels and last two are apart from each other, making her look like a 0-6-2.
- She also lacks siderods.
- Despite Yen being a Chinese engine, she is possibly named after the currency of Japan, the Japanese Yen.