The original script for Ichimatsu’s lines were written with incomprehensible symbols of ☆○△
× and other emoji, which Fukuyama Jun (CV: Matsuno Ichimatsu) interpreted in his own way to perform this scene here. He says in Osomatsu-san Radio #11 that he actually came up with a certain “rule” so that the words sound Japanese-ish. Fukuyama also said that even if no one else knew what he was saying, he spoke in a way that there was an actual logical conversation taking place between Ichimatsu and the other yankees, and the sadist invites everyone to figure out what Ichimatsu is saying.
Even after learning this though, fans still have no clear idea of what yankee-Ichimatsu is talking about. As Ono Daisuke (CV: Matsuno Jyushimatsu) said during Osomatsu-san Radio #10, even if you knew that there was a rule involved, you wouldn’t be able to decipher it since it’s hard to pick out what’s being said with that lisp and grunts anyway.