- “Oh, dear, no. It’s not good enough. Oh, yes, of course. Oh dear. Call this a railway? Huh. Dreadful. Every day something goes wrong. So predictable. Seats uncomfortable, trains always late. Oh dear, oh dear, oh dear!”
- ―The Grumpy Passenger
The Grumpy Passenger is a man who rides on Duncan's train everyday. The man is constantly complaining about everything. One day, Duncan decided he had had enough of the man and tried to do everything he could to stop the complaining. No matter what he did, the man still complained. After causing a lot of trouble, Mr. Percival told Duncan that he knew the man well: he was always extremely grumpy and finding something to moan about. Lesson learned, Duncan decided to ignore the man in future.
He is always checking his pocket watch, often reads the Sodor Times newspaper and carries a flask of tea. He is a fan of the Sodor United Football Team, and attended one of their games against Barrow.
Once, he took a tour of the Estate Railway. When the tour concluded, he attempted to disembark his coach, only for Stephen to set off in pursuit of Millie, after assuming that she had run away. Stephen took his train to the Blue Mountain Quarry, which the passenger complained about for "not being in the brochure". Stephen eventually ran out of water near Crovan's Gate, much to the passenger's fury. He attempted to complain to Sir Robert Norramby, only for the Earl to say he was lucky to receive an extended tour of the island at no extra charge. The Earl also promised him free tea and cake upon their return to the Estate, which placated the passenger.
As his nickname suggests, he is a very grumpy and moody man who always complains about something endlessly, with the railways he uses being a particular target, or even cause, of his ire. Very rarely is he seen in a good mood.
- Season 18 - Thomas and the Emergency Cable (cameo), Duncan and the Grumpy Passenger, Duncan the Humbug (cameo) and The Perfect Gift (cameo)
- Season 19 - Toad and the Whale (cameo), Very Important Sheep (cameo), Reds vs. Blues, Thomas the Babysitter and Goodbye Fat Controller (cameo)
- Season 20 - Blown Away (cameo) and Cautious Connor
- Season 21 - Runaway Engine, P.A. Problems and Confused Coaches
- The Great Race (cameo)
- Keith Wickham (UK/US)
- Kōichi Sakaguchi (Japan; Duncan and the Grumpy Passenger, Reds vs. Blues and P.A. Problems)
- Hiroo Sasaki (Japan; Thomas the Babysitter)
- Nobuaki Kanemitsu (Japan; Cautious Connor)
- Shōto Kashii (Japan; Runaway Engine and Confused Coaches)
- Jarosław Domin (Poland)
- Roberto Mendiola (Latin America)
- It is unknown what his name is.
- The Grumpy Passenger is a modified version of a generic background character who would later be used as a Great Railway Show Judge.