That was not Pooty being Playful, that was him warning Carlson that he knows him and his secrets, and if he veers off script, well...let's just say some of Carlson's deep hidden secrets may come to light.
But, of course, just Pooty doing the interview revealed a lot. It revealed that things are worse for Russia than Russia is acknowledging, because otherwise Pooty wouldn't be doing an interview in the first place.