Right around the time Michael and I got to Wisconsin (early this month), he adopted a new mannerism. This saying immediately improves any sentence. By way of example, here are two instances from today:
Scenario 1 -- we're in the car, listening to "Everywhere That We Go," which is one of those perpetual songs. The last line of the verse is "And if they can't hear us, we sing a little louder" and it gets repeated. But the last line of the whole song is "And if they can't hear us... they're deaf!" Michael's commentary: "You're deaf, mmm-hmmm, that's right!"
Scenario 2 -- Michael hurts Daddy's nose. "No, Michael, that's not nice!" Michael: "not nice... mm-hmmm, that's right!"
He also like to validate his own opinions. For example, he'll be sitting down eating some almonds and say something like "I love almonds. Yup, mm-hmmm, that's right!" Or he confirms a request. "I want nummies. Okay! Yup, mmm-hmm, that's right." Or if he knows that it's something that I usually say but he says it instead. "God bless Booku. Yup, mm-hmmm, that's right."