"I just wanted to know if there's something we could do that's not presidential," Fallon said, "something that we could do now that we're both just civilians. . . . Can I mess up your hair?"
He then proceeded to mess up Trump's hair.
Fallon's famous hair tousle, turning Trump into a disheveled-looking bedhead, and the rest of his lighthearted Sept. 15, 2016, episode resulted in accusations from Trump critics that Fallon was trying to "normalize" or "humanize" Trump amid his heated rhetoric assailing Muslims and Mexicans.
Fallon recently said the backlash made him depressed. So on Sunday, in between tweets about tariffs and immigrants, the president chimed in on Twitter to tell the comedian to "be a man."
Fallon, Trump said, "is now whimpering to all that he did the famous 'hair show' with me (where he seriously messed up my hair), & that he would have done it differently because it is said to have 'humanized' me-he is taking heat. He called & said 'monster ratings.' Be a man Jimmy!"
Trump's comments come after Fallon's June 19 interview with the Hollywood Reporter on its "Awards Chatter" podcast, in which he recounts the Trump episode that marked a low point in his career. He was not trying to "normalize Trump," he said, or to "say I believe in his political beliefs or any of that stuff." It was all just part of the "fun of the show." But fellow comedians "made fun of him" on Twitter, he said, making comments about his character that he said were hurtful.
"It was definitely a downtime, and it's tough for morale," he said in the interview. "There's 300 people who work here, and so if people are talking that bad about you and ganging up on you in a really gang mentality - it was insane. It was people you wouldn't expect. You go: 'All right, we get it. I heard you. You made me feel bad. So now what? You happy? I'm depressed. You want to push me more? What do you want me to do? You want me to kill myself? What would make you happy? Get over it.' "
He apologized "if I made anyone mad, and looking back, I would do it differently."
Fallon was quick to respond to Trump's tweet on Sunday.
"In honor of the President's tweet I'll be making a donation to RAICES in his name," he tweeted.
RAICES, the Refugee and Immigrant Center for Education and Legal Services, is assisting with family reunification legal services among undocumented immigrants separated from their children at the border under the Trump administration's "zero tolerance" policy.