Donald Trump and Jimmy Fallon are getting into it on Twitter, following revelations of the late night host's regret over a pre-election interview from 2016.

Fallon revealed to The Hollywood Reporter that he would've done the interview differently, after receiving immense criticism for giving the now-president a softball interview, which included a bit where the host messed up Trump's hair.

Amid furore over his administration's border policies and threats to trade partners, Trump tweeted his displeasure at Fallon's regret on Sunday, telling the TV host to "be a man."

Shortly after Trump's tweet, Fallon declared on Twitter that he would be donating to RAICES, a Texas-based educational and legal service for refugees and immigrants. 

The donation will be made under the president's name, in "honor" of the tweet.

Following the hair-ruffling debacle, Fallon's ratings have taken a tumble. The show has fallen behind relative newcomer (and a far more politically engaged) Stephen Colbert.

Fallon was chastised for "humanizing" Trump at the height of the 2016 Presidential campaign.

"I did not do it to 'normalize' him or to say I believe in his political beliefs or any of that stuff," Fallon told the publication. 

Fallon said the intense criticism following Trump's election had been demoralizing for himself and the 300 of the show's staff, especially as comedians from other shows joined in on the attack.

"It's all in the fun of the show. I made a mistake. I'm sorry if I made anyone mad. And, looking back, I would do it differently," he added.