I have a feeling that Oda re-used that gag as often as he did so that this moment held so much more weight and really emphasized that Luffy has gotten through to Momo and that something in Momo has changed. Luffy has challenged Momo to be the leader that he says he is – the leader that he has not been until this very moment. He has pushed Momo to take a stance as a Lord and to no longer just be pulled along by his Retainer’s decisions. He has influenced him to start making his own demands and requests and to speak for himself for the very first time . Luffy was the first person to treat Momo as if he were an adult. He’s shoved him forward on his path towards becoming a leader and this was Momo’s very first step. It’s something that Luffy has done time and time again.
Luffy is intelligent. He’s not the intelligent that a Logocentric society like many of ours holds on a pedestal. There are 9 kinds of intelligence and Logic is only one of them. Luffy’s intelligence lies with the heart. He understands human emotion. He understands what it is that people need in order to be pushed to the next level. He knows what to do in order to make people realize what’s important. He knows how to get people to express what they truly desire. To make people wake up to their faults or see the strengths they didn’t know they had. He sees the emotions in people that they don’t see in themselves. He knows when to hang back and wait for someone to come around. He knows when to stubbornly push forward until they give in. He may not know facts, but he knows himself and he knows others and I think that that is equally as important.