Comedian Stephen ColbertStephen Tyrone ColbertYang to give ,000 a month to Twitter user on Colbert Key endorsements: A who's who in early states McConnell dismisses latest Jon Stewart criticism: We 'never left' 9/11 victims behind MORE caught Sen. Rand PaulRandal (Rand) Howard PaulWe're all on the tarmac, waiting for an Iran policy This week: Congress set for clash on Trump's border request Washington braces for Trump's next move on Iran MORE (R-Ky.) off guard late Wednesday night, joking about marijuana.

“You’re not going to talk about pot, are you?” the GOP presidential candidate asked Colbert when the late-night host quizzed him about drug policy reform.

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“Are you a cop?” Colbert retorted. "Because if you’re a cop, you have to tell me. Otherwise, this is entrapment.”

“I thought we said before we would not talk about pot, Stephen,” Paul replied, wiping his brow with a kerchief.

“You tried to sell me pot backstage,” Colbert quipped. "Sorry, you tried to sell me on the idea of changing sentencing guidelines for pot backstage. I should have finished the sentence.”

Paul then turned more somber when discussing GOP presidential front-runner Donald Trump.

“I think, all kidding aside, that there’s a certain seriousness to leading a nation of 300 million people,” he said of the outspoken billionaire.

“He says, ‘Of course we’ve got a nuclear triad and our biggest problem is we haven’t been using it enough,’” Paul continued.

“We’re kind of making light but that shouldn’t be made light of. You want someone who has judgment, someone who has wisdom and someone who has restraint.”

Rand Paul also discussed his father, former Rep. Ron Paul (R-Texas), a two-time GOP presidential candidate.

“He’s doing great,” he said. "My dad is indomitable. We go home and he out-walks us, he out-rides us on the bike. He’s in great shape.”

Paul additionally joked about how his fiscal conservatism defines his spending habits, given he performs his own haircuts.

“I’m conservative, man — I’ve got to save money,” he said. "I have three kids in college.

“It’s a bit random,” the Kentucky lawmaker added of his barber skills. "Sometimes there’s drinking beforehand."