My mom pointed out that Elliot Sober did not, in fact, write the “If you had a brother, would he like potato pancakes?” joke. She says she heard it as a child from my great-grandfather. And it’s older than that: one version of the joke appears in the 1858 comedy Our American Cousin (most famous nowadays as the last play Abraham Lincoln ever saw.) The comic engine of Our American Cousin is the upper-class twit Lord Dundreary, who brought the house down with business of this nature:
Dun What do they keep in pigeon houses? Oh! pigeons, to be sure;
they couldn’t keep donkeys up there, could they? That’s the dairy,
Geo Yes, my lord.
Dun What do they keep in dairies?
Geo Eggs, milk, butter and cheese.
Dun What’s the name of that animal with a head on it? No,
I don’t mean that, all animals have heads. I mean those animals
with something growing out of their heads.
Geo A cow?
Dun A cow growing out of his head?
Geo No, no, horns.
Dun A cow! well, that accounts for the milk and butter;
but I don’t see the eggs; cows don’t give eggs; then there’s the cheese–
do you like cheese?
Geo No, my lord.
Dun Does your brother like cheese?
Geo I have no brother. I’m so delicate.
Dun She’s so delicate, she hasn’t got a brother. Well,
if you had a brother do you think he’d like cheese?