The one and only Graham Norton returns to BBC America (October 7), airing on Saturdays at 10/9c, a show famous for its relaxed chat and formidable line-ups.

This often gives rise to some surprising celebrity behavior, though, in his role as master of ceremonies, Graham is largely unflappable.

Some moments, however, are impossible to ignore, so to celebrate the return of The Graham Norton Show, we've compiled a list of some of the most shocking talkshow moments — ones that left even the host open-mouthed and unsure how to continue.

10. Meg Ryan clams up on Michael Parkinson

You can't blame Meg Ryan for not warming to British talkshow host Michael Parkinson. She admitted during a 2003 appearance on Parkinson that she didn't enjoy the spotlight, before launching into a butt-clenchingly awkward demonstration. Eventually things got so bad Michael asked Meg what he should do, and her advice came as a relief to everyone watching: "Wrap it up."

https://www.youtube.com/watch?v=blpq-Iwu25s

9. Dame Helen Mirren leaves Stephen Colbert speechless

"I suddenly can't remember any questions." Those are the first words Stephen Colbert uttered after receiving a rather seductive kiss on the lips from Helen Mirren during her appearance on his show in 2016, proving there really is nothing like a dame.

https://www.youtube.com/watch?v=n_kGkGUAKRw

8. The Bee Gees walk out on Clive Anderson

The Bee Gees' 1997 appearance on Clive Anderson Talks Back turned out to be much shorter than anticipated, when the brothers Gibb took umbrage at the talk show host's odd line of questioning. First Barry walks off, then Robin, until just Maurice is left on stage. Awks.

https://www.youtube.com/watch?v=VHa6vYq6Nyk

7. Kanye West cries in front of Jay Leno

Kanye West has never been one to hide his emotions, but his 2009 appearance on The Jay Leno Show took the cake. Days after he'd invaded the stage and interrupted Taylor Swift's acceptance speech at the VMA Awards, he appeared on the show looking contrite and visibly chastened — and then Jay brought up his recently deceased mother.

https://www.youtube.com/watch?v=A6bgSITBrVQ

6. Hugh Grant 'fesses up on Jay Leno

Hugh Grant was slated to appear as a guest on The Tonight Show in 1995 to promote new movie Nine Months. The trouble was, just two weeks before he'd been caught in a rather, uh, compromising position on Sunset Boulevard, while he was still dating Elizabeth Hurley. Jay started with the question that was on everyone's mind: "What the hell were you thinking?"

https://www.youtube.com/watch?v=vrJ2jc6qfzA

5. Mark Ruffalo challenges Jon Stewart

The Daily Show's erstwhile presenter Jon Stewart had many strengths, but watching his guests' films or reading their books before interviewing them was not one of them. During one of his final shows in 2015, Jon was surprised by Mark Ruffalo, who introduced a video collecting all his fake compliments together, before giving him a taste of his own medicine.

https://www.youtube.com/watch?v=9VhAYW1nHXE

4. Mark Wahlberg sits on Graham Norton's lap

When Mark Wahlberg appeared on The Graham Norton Show in 2013, many assumed he'd become a little too, uh, refreshed from the show's famously generous, um, beverage allowance for interviewees. As fellow guest Sarah Silverman gamely tried to finish her story about a childhood sleepover, he shifted along the sofa, got up, and eventually ended up on Graham's knee.

[bbca_video_embed media_id="537768003518" video_id="sqpAZnQjc0N1"]

3. Drew Barrymore flashes David Letterman

Say what you like about Drew Barrymore, but she's good at gift giving. In a notorious 1995 Late Show appearance, she got on top of David Letterman's desk, danced for him, and flashed him in honor of his 48th birthday. Now that's a nice present.

https://www.youtube.com/watch?v=6VMzn7XBSoM

2. Nicole Kidman admits she once tried to hook up with Jimmy Fallon

It's not often Jimmy Fallon is rendered speechless, but when guest Nicole Kidman revealed in 2015 that he'd passed up on the chance to date her, not only was he unable to speak, but he also went bright red and had to take a lie down.

https://www.youtube.com/watch?v=qtsNbxgPngA

1. Tom Cruise jumps on Oprah's sofa

Nicole's ex Tom Cruise was positively giddy when he appeared on The Oprah Winfrey Show in 2005. The reason? His burgeoning romance with Dawson's Creek star Katie Holmes, whom he eventually married and had a daughter with. The pair may have split since, but his happiness here is palpable — if a little disconcerting. Just watch Oprah's face from 09:33.

https://www.youtube.com/watch?v=nMj1DaJU-sY

Which moment will you be watching over and over for years to come?