In their first appearance, 'Arry and Bert crept alongside a lonely Stepney, who had mysteriously been sent to the smelters by mistake. They shunted Stepney into the larger smelting shed underneath a giant grabber, and threatened to scrap him. Thankfully, Stepney was saved by the Fat Controller, once the diesels had left.
Despite being villainous, 'Arry and Bert are also known for playing tricks on steam engines, such as making them "Middle Engines". Once, they shunted trucks in front and behind Percy. This later led Percy to being pushed onto the coal tipper by mistake. Later, 'Arry and Bert played the same trick on James. Sometime later, they frightened Fergus away from the smelters, and bullied Neville, which made the engines think he was planning to bump them.
On some occasions, 'Arry and Bert's teasing ways backfire. Once, they played a ghostly prank on Thomas and Emily during Halloween, though they ran away when they thought Emily was a ghost. Another time, 'Arry and Bert teased Percy for having a whistle. Percy paid them back by creeping up behind them and blowing on his whistle. Later, along with Diesel, 'Arry and Bert began teasing Thomas for being smelly, but were later covered in stinky cheese.
'Arry and Bert were also part of the group of diesels that took over the Sodor Steamworks. They later teased Henry because of the coal he had to use by calling him "Mr. Special Steam". They also laughed at Gordon after he ran into Diesel's flatbed and damaged his buffer beam.
In the twentieth season, 'Arry and Bert liked being rough and tough along with Diesel, they realized Diesel was trying to be nice to everyone. So Thomas took 'Arry and Bert to the ducklings while Diesel followed behind them. Diesel, 'Arry and Bert then realized the ducklings were cute.
'Arry and Bert are unquestionably devious and scheming. They feel superior to steam engines and, working at the scrap yards, they enjoy the chance to break up engines, or at least make their lives more difficult. Due to their grim task, they have earned a reputation on Sodor as "The Grim Messengers of Doom."
'Arry and Bert also have a tendency to act scheming, slimy, greasy, and oozy. According to their merchandise bios, they wish to scrap Oliver and Stepney, who have both escaped the cutter's torch once before.
However, despite their prejudices, the diesels have cooperated with steam engines on occasions, and when they are in trouble, steam engines often come to the rescue.
they played Lady And Tramp In 'Arry and the Bert and 'Arry and the Bert 2: Diesel 10's Adventure
'Arry is a Beautiful Cocker spaniel And Bert is a Street Mutt
They played Marv and Harry in Home Alone and Home Alone 2: Lost In New York
'Arry is Harry and Bert is Marv
They played Crabbe and Goyle in the Harry Potter movie series
'Arry is Vincent Crabbe and Bert is Gregory Goyle
'Arry and Bert are based on BR Class 08 diesel-electric shunters. Over 70 members of this class survive today in preservation, while around 100 remain in service on the national rail network. They were in fact the most successful shunting engines in the world, with 996 of them built. Devious Diesel, the Diesel Shunter, Splatter, Dodge, Paxton, Sidney, Ulli and the Mainland Diesels are also members of this class.
'Arry and Bert are painted green-grey with yellow hazard stripes on their fronts with yellow cabs. They have "Sodor Ironworks" written on their sides in white.
- Stepney was all alone, but not for long. 2 diesels approached.
- "Got you/ya this time, Stepney. You'll make very fine scrap indeed, buffer him, Bert!"
- The Diesels took him to the Large Smelting Shed.
- "Bye-bye, Stepney!" said the Diesel. (laughs in US version)
- 'Arry and Bert's introduction, "Stepney Gets Lost", 5th season
- The Next Day, James arrived at the Smelters. He was determined not to be tricked by 'Arry and Bert.
- "Hello/Hallo, James!" oozed Harry. "Come to learn a thing or 2 from those who know?!"
- "Just get my trucks ready, and stay out of my way!" huffed James importantly.
- "Yes, Sir," Bert chimed greasily.
- James meets 'Arry and Bert, "Middle Engine", 6th season
- Fergus and his driver arrived at the Smelters.
- "I want to go back to the Cement Works! None of the Other Engines like coming here, its so scary!"
- "You're right!" said his driver.
- Just then, the Scrap Diesels emerged.
- "Hello! Are you happy to be here?"
- "No!" cried Fergus.
- Fergus meets 'Arry and Bert, "Fergus Breaks the Rules", 7th season