BoCo is a large green diesel.
BoCo is one of the older, but kinder engines on Sodor. He is fair, but firm and always maintains his authority, as he, Marion and Edward are the only ones on Sodor who can keep Bill and Ben in order. When he first came to Sodor, the latter mentioned twins played a trick on him when he took their cars by mistake. Ever since then he has been good friends with the two, as well as all the other engines on Sodor. Some engines were suspicious of him at first since he was a diesel, but they eventually saw BoCo's true colors and warmed up to him.
All of BoCo's third season appearances will be listed here once Season 3 is completed.
- BoCo was the first protagonist Diesel introduced in the series