- "If I were under me own power I'd bust ye both to smithereens!"
- ―Douglas talking to ‘Arry and Bert, Lift Bridge
‘Arry and Bert were purchased in 2001 to work at the Sodor Ironworks by Sir Frederick Aura, where they almost managed to incinerate Stepney the Bluebell Engine, who was trying to get home. Luckily, he was later saved by the Fat Controller, but Aura and the diesel twins were never discovered for messing with Stepney at the Smelter's! During their career, the Fat Controller and Aura established a contract of "joint ownership" where the diesels could be called upon to help on the Fat Controller's Railway. The diesels did not take this development warmly, and caused a great deal of mischief for the other engines. Thing escalated even further when Bert jammed the Vicarstown Yards Transfer Table later that week!
‘Arry and Bert where present whilst Arthur and Wilbert where working on the Little Western extension, and drove by the assembled James, Oliver and Toby, taking the opportunity to insult them. Later, they attended a secret meeting between the Lumberjacks and Ricky Mason, and speculated what Aura had planned.
The pair was planted at the Ministry of Defense Complex by Aura prior to the munitions incident. Aura instructs them to at least appear to be working on the outskirts of the compound, allowing for Mr. Richards and himself to make a quick getaway following the detonation.
One of the most devious schemes from this duo is one that involved the scrapping of a engine by the name of Patriot under the orders of Sir Frederick Aura. Patriot was brought to a furnace and turned into scrap while his driver and fireman were killed by ‘Arry and Bert's drivers. The incident was not brought to the knowledge of Sir Topham Hatt because all the witnesses not on the side of evil were killed.
When the Flying Scotsman and Gordon were double-heading an important train, Harry and Bert passed the two on their way from Vicarstown. The people in ‘Arry's van were Ricky Mason, Walter Richards, and one of Aura's henchmen, who held up a signal box so D261 and D199's runaway would hit Walter Sliggs' refinery.
‘Arry and Bert are very sneaky and devious, usually following orders from Sir Frederick Aura and disobeying those of Sir Topham Hatt. They refer to themselves as "Sodor's Grim Messengers of Doom." They are terrified of Sir Frederick Aura for obvious reasons, and follow his commands without question. They love to melt down steam engines, as ‘Arry and Bert both see them as a fading light in the dark that should cease to exist from their point of view.
- Season 1: Lift Bridge, Swagger and Swerves (cameo), Stepney Makes an Entrance (‘Arry or Bert cameo), The Old Warrior (‘Arry or Bert cameo), Redemption (cameo), Feeling Lucky?, Rising to the Occasion (‘Arry only (cameo)), Snow Blind (remastered version only), Buffer Bashing (‘Arry only (cameo)), Rendezvous with Disaster (‘Arry only (cameo)), Will Power (Bert only (cameo)), Conspiracy Theory
- Season 2: Paxton and Norman, Grim Messengers of Doom, Scot-free (cameo), Rosie (cameo), James Goes on a Trip (‘Arry only (cameo)), Rock-Star, Tag-Team, Munitions, Hibernation, Aura of Menace, Swashbuckler, Dead End (flashback (do not speak)), Thomas and the Fortune Teller (cameo)
- Season 3:Culdee Fell (cameo)
- Web Clips: Mike and Frank Banter: SLOTLT, ScarletFire, and EE93's Return (‘Arry or Bert cameo), Emily, Toby and Henrietta - Meet the Characters! (cameo)
- ‘Arry and Bert could be considered the main engine antagonists of the series since they are working for who could be considered the most villainous character in the series, that is Sir Frederick Aura, as well as "killing" trespassers such as Patriot and his crew.
- ‘Arry and Bert were originally played by a basketball player at EE93's school, but since Rock-Star, they have been played by TheKipperRunsAgain.