I think it is a reference to Gödel's incompleteness theorem.

> What is the ordered pair whose first member is the best question to ask, and whose second member is the answer to that question?

Is isomorphic to:

> What is the highest cardinality set in the set of all sets?

"What is the best question in the set of all questions?" is itself "what is the best question in the set of all questions?"

"What is the highest cardinality set in the set of all sets?" is itself "the set of all sets".

"What is the answer to that question?" is an assumption of bounded size, and therefore isomorphic to saying "the largest set that is not itself."

> What is the answer to the best question we could ask?" Which was roundly criticized because of the possibility that the answer would give no hint to the question it answered. One philosopher cheekily pointed out that the angel might reply "42 of course."

42 is a valid answer because if you assume two contradictory statements are true at the same time, then all statements are true. The cheeky philosopher is pointing out that "What is the answer to the best question we could ask?" implies self reference, which implies a contradiction.

The philosophers asked a self referential question and got a self referential answer.

At least that's my take.

There is (of course, philosophers are involved) some debate about whether the angel's answer is a valid answer to the question.

I feel like there's something deeper to it, since there's some recursion to the answer.

But it's not a joke about programmers, so I don't get it either, ha!