After more than three decades as a beloved talk-show host, Conan O'Brien has revealed the worst 'amateur move' a guest can make.

Conan was himself appearing as a guest on Hot Ones, the smash hit YouTube series where celebrities answer questions while eating progressively spicier wings.

The 60-year-old, who by his own admission grew up eating 'tasteless' food and is unused to spice, bravely attempted to retain his composure on Hot Ones.

In the course of his episode, Conan shared his expert opinion about what a talk-show guest can do to drain the energy out of an interview.

'The worst thing a guest can do is tell the audience it's not going well,' the television icon explained. 'I've seen it happen many times.'

After more than three decades as a beloved talk-show host, Conan O'Brien has revealed the worst 'amateur move' a guest can make

Conan was himself appearing as a guest on Hot Ones , the smash hit YouTube series where celebrities answer questions while eating progressively spicier wings

Conan added: 'It's an amateur move because the host can do a lot to let people think it's going great even if it's not. There are many things the host can do. The host can be enjoying. The host can act a little bit. The host can do things.'

He argued that 'audiences wanna see a good show and 'a good interview,' adding that he was 'always amazed' when guests would remark that they were bombing.

Such a guest would 'be doing okay, and they'd make a couple of jokes, and it's fine, and then they would just go: "Ugh," and they would look right out to camera, and they would say: "Ugh, this just isn't going very well, is it?"'

Conan would then 'look out at the audience, maybe 200 people sitting there, and see 200 souls leave 200 bodies and float up through the ceiling,' he joked. 

'Because they were just told they were not getting a good show. No, that's not show business! Show business is: "You're getting the greatest show in the world."'

Conan's appearance on Hot Ones dropped just one day after he made his first appearance on The Tonight Show since being fired from it in 2010. 

''It's weird to come back,' he told current host Jimmy Fallon. 'It's weird. I haven't been in this building for such a long time, and I haven't been on this floor in forever.'

He became a beloved talk-show host in the 1990s on Late Night With Conan O'Brien, which followed The Tonight Show With Jay Leno on NBC.

He became a beloved talk-show host in the 1990s on Late Night With Conan O'Brien, which he is pictured on in 2004, five years before he left

In 2009, after waiting 16 years to finally take on the mantle, Conan was finally able to become the host of The Tonight Show (pictured) when Jay Leno bowed out

Conan's appearance on Hot Ones dropped just one day after he made his first appearance on The Tonight Show (pictured this week) since being fired from it in 2010

In 2009, after waiting 16 years to finally take on the mantle, Conan was finally able to become the host of The Tonight Show when Jay bowed out.

However, Jay suddenly proved unwilling to leave the world of late-night television, and launched a talk-show on NBC that aired every night right before Conan.

The battle of wills between Jay and Conan became a legendary feud that played out dramatically across the headlines for months. 

Conan was ultimately fired by NBC in 2010 - getting an almost $40 million payout in the process - and Jay returned to the The Tonight Show, triumphant.

In short over, Conan moved over to cable with a successful talk-show on TBS, which enjoyed a long run from 2010 until 2021.