'I really don't know what I'm doing!' Conan O'Brien lights up a JOINT with notorious pothead Seth Rogen as he prepares to end his long-running TBS late night show

Conan O'Brien doesn't smoke marijuana very 'often' but when he does, he does it in front of the camera and with Seth Rogen. 

Seth was a guest on the 58-year-old's TBS show on Tuesday night and doled out some helpful advice for Conan for what to do when the show comes to an end: get high.

Back in 2020, O'Brien announced that his self-titled late-night show would end in June 2021 after nearly 30 years. 

All for a laugh: Conan O'Brien took a hit off of Seth Rogen's joint during Tuesday's episode of his late night show

'I'm not even kidding, I don't really know what to do with downtime,' Conan admitted to the actor.

'I would suggest—this is going to be hilariously on-brand—try smoking a lot of weed for a long time,' Rogen advised when asked how he thinks the host should spend his free time. 

'Try it,' Seth went on, adding that Conan didn't strike him as someone who smoked pot very often. 

'I don't smoke any weed  - and that's not a judgement,' O'Brien responded. 'I enjoy my lucidity.'

 'I don't smoke any weed - and that's not a judgement,' O'Brien responded. 'I enjoy my lucidity.'

'I would suggest—this is going to be hilariously on-brand—try smoking a lot of weed for a long time,' Rogen advised when asked how he thinks the host should spend his free time after Conan ends

Rogen busted out laughing when Conan referred to marijuana as a 'fine herb.' He quipped: 'If there was ever a sign you didn't smoke weed it's that you just called it a "fine herb."'

As it turns out, the Neighbors actor actually owns a pot company so when Conan asked what type of product he would suggest, Rogen pulled a joint, ready to go, right out of his suit jacket.    

Always ready for a good comedy bit, Conan agreed to spark up the doobie - which the ginger haired star first hilariously mistook for a 'birthday candle.' 

'Well, what is this?' Conan asked. 'What is it really?' 

Expert advice: Seth strongly advised O'Brien to take just 'one hit' of the weed - intimating it was strong stuff - and promised him a 'good time'

Rogen busted out laughing when Conan referred to marijuana as a 'fine herb.' He quipped: 'If there was ever a sign you didn't smoke weed it's that you just called it a "fine herb."'

'This is the kind of thing you do when you know its over for you,' Conan laughed before lighting up. 'I really don't know what the f**k I'm doing.'

'That is weed,' Seth said, obviously.

'I know its weed! I didn't think it was pencil shavings,' Conan responded. 

Seth strongly advised O'Brien to take just 'one hit' of the weed - intimating it was strong stuff - and promised him a 'good time.' 

'This is the kind of thing you do when you know its over for you,' Conan laughed before lighting up. 'I really don't know what the f**k I'm doing.'

Doobie newbie: Always ready for a good comedy bit, Conan agreed to spark up the joint- which the ginger haired star first hilariously mistook for a 'birthday candle.'

Too funny: Rogen and O'Brien ended up in hysterics before the pot was even lit after the Superbad star admitted he was 'so nervous' about the whole thing, especially since Conan was holding the joint the wrong way

Puff, puff, pass: O'Brien successfully lit it up, took a hit and politely passed it down to Seth who then shared it with sidekick Andy Richter

Rogen and O'Brien ended up in hysterics before the pot was even lit after the Superbad star admitted he was 'so nervous' about the whole thing, especially since Conan was holding the joint the wrong way. 

O'Brien successfully lit it up, took a hit and politely passed it down to Seth who then shared it with sidekick Andy Richter. 

'I'm so happy with what just happened,' Seth cheered. 

Conan, for his part, claimed he wasn't really feeling the effects but was laughing 'too long' at some jokes.  

'I'm so happy with what just happened,' Seth cheered.

Hysterical: Rogen gushed over the once-in-a-lifetime moment on Twitter after the show

'I smoked weed with @ConanOBrien his show and was legit terrified that I got him too high haha. (This was a surreal and shocking moment for me and was genuinely unplanned),' Rogen later gushed on Twitter. 

This month will see the end of Conan after 28 years, 11 of them on TBS. 

'In 1993 Johnny Carson gave me the best advice of my career: "As soon as possible, get to a streaming platform." I'm thrilled that I get to continue doing whatever the hell it is I do on HBO Max, and I look forward to a free subscription,' O'Brien joked when he made the announcement. 

O'Brien has fronted 1,400 of the shows for TBS after his departure from The Tonight Show.

He famously came to the cable network in 2010 from NBC. There he had hosted 'Late Night with Conan O'Brien' for over 15 years before he was tapped to take over 'The Tonight Show' from Jay Leno.

However, after NBC attempted to move the primetime series 'The Jay Leno Show' to late-night and push back 'The Tonight Show' to the 12.05 am timeslot, O'Brien quit the show rather than 'participate in what I honestly believe is its destruction,' he said at the time. 

End of an era: This month will see the end of Conan after 28 years, 11 of them on TBS - he will move to HBO Max