At the time, Fallon was roundly criticised for pandering to Trump (before he was elected) instead of asking him tougher questions or challenging him in any way - with one critic suggesting that he had lost the 'last shred' of “any credibility as a thinking comedian with a point-of-view”.
In recent days, Fallon has spoken about his regret regarding the show - which of course, mortally offended Trump, who took to Twitter to denounce the "whimpering" talk show host, and demand that he "be a man":
.@jimmyfallon 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 now done it differently because it is said to have “humanized” me-he is taking heat. He called & said “monster ratings.” Be a man Jimmy!
— Donald J. Trump (@realDonaldTrump) June 25, 2018
Fallon's response, meanwhile, was simple but effective:
In honor of the President’s tweet I’ll be making a donation to RAICES in his name.
— jimmy fallon (@jimmyfallon) June 25, 2018
Here's a reminder of the incident, if your memory needs jogging: