Smudger was very cocky indeed and rode dangerously, which led to his ultimate downfall. The Mid Sodor controller took his wheels away and made him into a generator. Duke had did his best to keep the fiesty little engine in line, but to no avail. In his heyday, Smudger had a plethora of accidents and caused a great deal of damage. To his day, Duke seems to be obsessed with recollecting on Smudger's various mishaps.
It is excepted that Smudger was left in the back of the shed when Duke was rescued.