|This article is about the Story Library book. You may be looking for the diesel engine.|
- "I'm a really lazy engine!"
Dennis (later re-titled, Dennis the Lazy Diesel and Thomas the Helpful Engine) is the forty-eighth book in the My Thomas Story Library series.
On his day off, Thomas is tricked into doing Dennis' work.
- Dennis is incorrectly illustrated with spoked driving wheels, a grey crankshaft, navy wheels, and a red running board.
- Throughout the book, Dennis is missing his number.
- In the first illustration, Percy's coal bunker is missing and his siderod is not connected to his piston.
- In the third illustration, Dennis' coupling rods are out of alignment.