It takes him a moment to think through. Luka's entirely focused on answering the question correctly at first, but as he pieces through all of the Protector's hints, he picks up on the message.

"A childish insult about you... hmmm," Luka taps his chin, as if deep in thought. He is in fact deep in thought, but he's wondering just how to get Four properly distracted. "The Protector... is... a...."

Luka absentmindedly feels the length of the ceremonial sword's hilt as he tries to conjure up a suitable childish insult. He was eager to make use of the thing, if he could.

"...butt head?"