The "Curb Your Enthusiasm" star and Elmo were guests on the "Today" show Thursday when Larry got physical with the "Sesame Street" puppet. It was all in good fun, of course, but yeah -- he kinda got handsy with the red muppet.

Elmo was just wrapping up a segment about his viral mental health pop-in when Larry walked over and put both hands on Elmo ... smashing his face in, and taking a swipe at Elmo's dad, Louie.

Hoda Kotb, Savannah Guthrie and Craig Melvin were trying to throw it over to Al Roker for a weather report ... but Larry had other plans.

The anchors quickly took sides with Elmo ... with Savannah telling Larry he'd gone too far and Al saying he wasn't surprised by Larry's actions.

Larry's response ... "Somebody had to do it!!!"

Unfazed, Elmo told Larry to come back and talk about how he feels ... with Louie making it a teaching moment. Larry apologized before his segment on the upcoming 'Curb' season ... saying sorry in true LD fashion.

Savannah asked Larry to speak from the heart, with Larry hilariously responding ... "From where? What organ are you talking about?"

The agonizing apology felt straight out of a 'Curb' episode ... and Elmo accepted. We gotta say ... Larry's doing a masterful job promoting the final season. He's very much in character in real life.