Don't touch the hair! Jimmy Fallon went where no TV host has gone before on Thursday, September 15 — the Tonight Show star got his hands on Donald Trump's hair.

The Republican presidential candidate made his third appearance on the NBC talk show since announcing his candidacy in June 2015, and while he didn't do a sketch with Fallon playing the former Apprentice star this time around, Trump did agree to let Fallon mess up his hair.

The real estate mogul's trademark coiffure has been a minor star of the campaign, with Trump even asking a woman to tug as his long locks last year to prove "it's my hair" and not a toupee.

On Thursday, Fallon asked Trump, "Can I mess your hair up? I'll be gentle."

After the GOP nominee reluctantly agreed, the Saturday Night Live alum didn't just tug on that carefully lacquered 'do, he mussed it. And he mussed it good.

The pair also discussed his upcoming debate against Democratic presidential nominee Hillary Clinton on September 26, and Trump's praise of Russian president Vladimir Putin, with Fallon joking that the pair's bromance needed a nickname. His choice? Vlump.

Trump, who has previously talked about his admiration for the former KGB spy, backpedaled as he spoke to Fallon on Thursday.

"Look, I don't know him, and I know nothing about him, really," Trump said. "I just think if we got along with Russia, that's not a bad thing. The Democrats are trying to say I like him. I don't like him. I don’t dislike him. I don't have any feelings one way or the other. And it's not going to matter what he says about me. If he says good things or bad things about me, I'm going to make great deals for our country."

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