What we're watching: Jimmy Fallon vs. Trump's tweets

NBC’s Tonight Show host Jimmy Fallon responded on air Monday night to a Trump tweet, asking his audience: “shouldn’t he have more important things to do?”

Flashback: Trump's tweet — saying Fallon was "whimpering to all that he did the famous "hair show"" and calling for Fallon to "be a man" — came after Fallon expressed regret for messing with Trump's hair in a September 2016 interview on his show.