Dennis is a lazy diesel who dislikes hard work, but enjoys making other engines do it for him. He has a twin brother called Norman.

Dennis is considered to be a very lazy diesel who tries to take advantage of others and depend on them to do his work instead. Dennis will often create excuses to get out of work and is infamous for the fact that, unlike most of the engines on the railway, he does not make an effort on being really useful, and slacks off on a regular basis. As a result of his laziness, he is very unpopular with other engines, but they are forgiving enough to let him redeem himself, depending on how motivated he really is. He usually gets caught in his lies and always says sorry - but whether or not he means it is the question.

His voice source is freelanced as long as it’s within the age range.