Diana and Dolly are two Australian twin engines. They will debut in The New Railway Series.
Diana is the older of the two twins. Unlike Dolly, she doesn't act Australian at all, but still has the accent, she's also calm and sensible. However, she's a major softie and is easily embarassed. Diana is confirmed to have a crush on Douglas.
Dolly is the younger one. She is very Australian, unlike Diana. On a side note, she's a lot more crazy and silly. Her and Donald always try to peek on Diana and Douglas, thinking they are dating, which they're right. But, they always fail. She's Donald's best friend.