Kathryn Hahn reveals adorable behind-the-scenes fact from The Holiday

Speaking to RadioTimes.com in an exclusive Big RT Interview, Hahn said that she was pregnant in real-life whilst playing Amanda's (Diaz) pregnant assistant Bristol – even though her baby bump in the movie was fake.

When asked whether she watches the film every Christmas, Hahn said: "Yes, I do! And I'll tell you a little secret about it – I played a very pregnant assistant of Cameron Diaz in the very beginning. I'm in there for like three seconds, maybe a little longer, maybe three minutes.

"But John Krasinski also plays her editor so we had a scene together – that's where I met John Krasinski, who was so lovely – and I had to wear this big prosthetic pregnant belly.

"But what I got to share on the set – I don't think to everybody, just a few people – was that I actually had a little baby in there. I actually was pregnant on set but then I was wearing a huge prosthetic belly on top of it. It was a very surreal experience.

"It's very weird to see that movie and be like, 'Oh my God, so funny.' I could kind of imagine what it would feel like."

She added: "My 15-year-old son is not as excited about it as my 12-year-old daughter!"

The romcom follows two women from opposite sides of the Atlantic Ocean – journalist Iris (Winslet) and movie trailer executive Amanda (Diaz) – who decide to swap houses for the Christmas holiday in order to get over their respective break-ups.

However, Amanda soon bumps into Iris's charming brother Graham (Law), while Iris becomes close with film composer Miles (Black).

You can read the full chat with Kathryn Hahn in her Big RT Interview. Looking for something to watch tonight? Check out our TV Guide.