'Arry and Bert are gruff diesel twins who work for the Sodor Ironworks at the smelters yard. They have attempted to scrap several steam engines without success.
'Arry and Bert are rather devious and scheming diesels. After Stepney was diverted onto a wrong track, the twins attempted to scrap him; but were stopped at the last moment by Sir Topham Hatt. They later shunted trains in front and behind Percy and James making them "Middle Engines". They later have come to respect the steam engines.
- The white outline around Bert's mouth is thicker than 'Arry's, which is ironic because Bert is said to have more stubble.
- 'Arry is the second HO engine to have a CGI face, the first being Diesel and Bert being the third.
- 'Arry and Bert's models are identical to Diesel's, but without the ladders, different paintwork and different faces. They are also fitted with brake pipes when they do not have in the TV Series.
- 'Arry and Bert are referred to as "Iron 'Arry" and "Iron Bert" on their packaging and the online store.
- HO Scale