Having been a stage manager I can tell you - without fail, no comedian ever does an original joke. Everyone of them I worked with did the same routines EVERY night. I know it looks fresh & spontaneous, but so does "Blue Man Group." but in fact the lines are always 90% scripted - it is just the target's reaction that is different every night.
We know John Heald doesn't really meet a Dick Johnson every cruise. But the jokes are the same.