Dennis is a lazy diesel who will do anything to get out of working. He takes advantage of any opportunity to create an excuse to avoid a decent day's work. When he's found out, he’s sorry — until the next opportunity to avoid work comes along.
Dennis and Norman are based on a British Rail 11001 Diesel Locomotive prototype built by British Railways Ashford. It was designed for shunting and mainline duties with a top speed of only 43mph!