Joker joke

The change from P to J in poker to joker is a punch line of word games, and the person who answers the question is also very witty. Using the same rules of word game, that is, by changing an initial, he answered a sentence. Jo-Incident changed J to C, which means co-Incident = coincidence, which means pure coincidence.

That is to say, Phoebe borrows poker to say that poker players are humorous (joker is a clown), and clowns are puns, that is, the king of poker (cat) and clowns (clowns). And Phoebe gave him a tit-for-tat, saying, that's not necessarily true, even if it is, it's just a coincidence.