Answer: Capricorn
Mom: "Capricorn, eh; what are they like?"
Magi: "He is the son of God, our Messiah, King of the Jews."
Mom: "That's Capricorn, is it?"
Magi: "Oh, no, no, no, that's just him."
Mom: "Oh, I was going to say, otherwise there'd be a lot of 'em."
I don't know which is funnier; the fact that mom has no idea why her brat is the object of praise, or that these so-called "wise men" don't know they've stumbled into the wrong stable.