As I'm a Limey, I feel a bit out of order suggesting this, but have you never heard the "Arkansas Traveller" with the dialogues between the "Old Man" and the "City Slicker Traveller". The way I've heard it performed, only the "A" part is played (with the jokes in between) until the very end when the the "B" part finally gets played.

Bits that I can remember (I'm probably starting something now!) go:

SS: "Say old man, can I take this road to .....?"
OM: "Nope ain't no use taking this road to .... - they already got one there".

SS: "Say old man, does this road fork round here somewhere ?"
OM: "Dunno about fork - but jest over that ridge it splits all to pieces!"

SS: "Old Man - you don't seem very clever to me".
OM: "Nope - perhaps not - but I ain't lost !"

SS: "Could you put me up for the night old man"
OM: "Only in the barn and the roof leaks"
SS: "Why don't you mend it then ?"
OM: "Every time I go to mend it, it's always raining"
SS: "Why don't you mend it when it ain't raining ?"
OM: "Coz it don't leak then !"

SS: "Say old man you lived here all your life ?"
OM: "Not yet !"

SS: "Say old man - will I be able to ford that river over there ?"
OM: "Don't see why not - my ducks done forded it this morning - and it only came up to (indicating waist) on them !"

SS: "Say old man - how'd like to buy this horse ? - runs five miles without stopping"
OM: "Wouldn't be much use to me - only three miles into town - have to walk two miles back !"

SS: "Do you live here alone old man ?"
OM: "Nope my son lives with me - he's out hunting"
SS: "What hunting on the sabath - don't he fear the Lord ?"
OM: "Nope - he takes his gun wherever he goes !"

SS: "Old man I can't see much between you and a fool"
OM: "Nope - a banjo and a fiddle's all I can see" (depends on instruments)

SS: "Say old man - why don't you play the other half of this tune ?"
OM: "Do you know it stranger ? - I'd be indebted if you could learn it me"
("B" part of tune etc.)

It's always the short punch lines the get the biggest laughs ie "Not Yet !"