“Nǐ Hǎo Thomas!”
- ―An An and Yin-Long greeting Thomas.
Number One Engine is the first episode of the twenty-second series.
While working on the Chinese Railway, Thomas is late picking up An An and Yin-Long. Later on when he is working on the line, he brags to them about being the fastest No. 1 engine, but Hong-Mei begs to differ that she is the No. 1 engine. The two of them decide to race together to see who is the fastest, but while racing Thomas is going too fast on a different track and is not looking, so he derails and realises how silly he is. Hong-Mei soon comes to help Thomas back onto the tracks and both the engines realise that it is okay for both of them to be No. 1 engines.
- Yong Bao
- An An and Yin-Long
- A Guard
- Annie and Clarabel (fantasy)
- Sir Topham Hatt (fantasy)
- The Mainland
- Island of Sodor (fantasy)
- Vicarstown Bridge (fantasy)
- Joseph May as Thomas
- Teresa Gallagher as Annie and Clarabel
- Keith Wickham as Sir Topham Hatt
- Dan Li as Yong Bao
- Chipo Chung as Hong-Mei
- Siu-see Hung as An An
- Windson Liong as Yin-Long and the Chinese Guard
- This is the first episode of several things:
- The first episode released under the Big World! Big Adventures! rebrand.
- The first episode that uses the Friendship in Motion intro and outro titles.
- The first episode to feature an on-screen character (Thomas) as the narrator and the first production since Thomas and the Magic Railroad to have a first-person narrative.
- The first episode that does not take place on Sodor and the first episode to take place in China.
- The first episode to feature fantasy sequences.
- Yong Bao's first appearance in an episode.
- The first episode since the twelfth series episode, Best Friends to have a running time of seven minutes.
- The first episode since the twentieth series episode, Skiff and the Mermaid to be dubbed into German.
- The first episode since the fifteenth series episode, Fiery Flynn to be dubbed into Finnish.
- Siu-see Hung and Windson Liong join the cast.
- Sir Topham Hatt as the moon is a parody to the moon in Le Voyage dans la Lune.
- Before its UK broadcast, this episode was shown at the Princess Anne Theatre (BAFTA) in London alongside Forever and Ever, What Rebecca Does and Banjo and the Bushfire on Saturday September 1st, 2018.
- On Nickelodeon in the US, this episode was originally due to air with Thomas in the Wild, but What Rebecca Does was featured instead. Future reruns, Nick On Demand and the Nick Jr. website feature the correct episode. Sometime later, it was repaired with Forever and Ever in the airings.