Complex sentence: Cletus was introduced during the fifth season of the whow, in "Bart Gets an Elephant", as one of the "slack-jawed yokels" gawking at Bart's elephant Stampy.
Split into simpler sentences: Cletus was introduced during the fifth season in "Bart Gets an Elephant". He is shown as one of the "slack-jawed yokels" gawking at Bart's elephant Stampy.