Quite the comedic duo those two. There are so many great exchanges.
One of my favorites comes from Exodus 21:22 where Doc is coming out of the Post Office checking his mail and Festus walking the boardwalk eyeing the ladies and wham! The mail goes flying.
Doc: Well I might have known it was you. You are an absolute and utter walking catastrophe. Ever since the day you first set foot in this town it's been nothing but complete chaos. There's no place I can get away from you in Dodge City. There's just...no place I can hide. Neither snow nor rain nor heat nor gloom of night can stop these couriers in the swift completion of their appointed rounds. But Festus Haggen can!
Festus: It isn't snowin' or rainin', Doc.