Donald and Douglas the Scottish Twin Engines

Donald and Douglas are black tender engines that are also twins that work on the North Western Railway.

Why They Rock

They were the first twin engines to arrive on Sodor.
They are very enjoyable and entertaining to watch.
Even though they bicker a lot, they refuse to be separated and decided go to Sodor together.
Their Scottish accents fit their personalities very well.
Whenever there is an episode we see them bicker, they always apologize to each other after they get in a fight unlike how Bill and Ben do.
They also got to return to the show since "Sodor’s Legend Of The Lost Treasure" with the help of Andrew Brenner.

Even though they did return in the Andrew Brenner era, they don’t get that much spotlight. Plus, their bickering in "Emily in the Middle" did get rather annoying.
In the US version of Season 6, they dropped their Scottish accents because of the toned down narration from Alec Baldwin. What happened to you in the Thomas series, Baldwin?