Kristen Bell was caught pumping breast milk during a read-through of the 'Bad Moms' script.

The 37-year-old actress starred in the 2016 comedy movie alongside Mila Kunis, Kathryn Hahn and Christina Applegate, and during an appearance on 'The Ellen DeGeneres Show', Mila revealed just how close-knit the cast is.

She shared: ''Kathryn and I are next to each other and K.Bell's just on a giant screen Skyped in. And as we're reading the script you see her face just getting closer and closer into the screen and the rest of her body going out of the screen. It was just a giant face. Then you hear this...''

Mila then started imitating a buzzing noise, and Kristen - who has daughters Delta, two, and Lincoln, four, with her husband Dax Shepard - continued the humorous story.

The blonde beauty, who has rejoined the duo to star in 'A Bad Moms Christmas', explained: ''I didn't know I was on a movie projector. I would have loved a heads up. I thought it was like, 'We're going to Skype in. It's going to be on a computer.' And I was home because I wasn't going early because I still had a little one and I needed to pump.

''And I'm sorry when you gotta do it, you gotta do it. And I thought, 'They're not going to care, also it's not going to be very loud.' Again, I didn't' realise I was on a 200-inch screen on speakers in a conference room. I thought it was someone's computer.''

However, not everyone involved in the Skype call was fully aware of what Kristen was up to.

She recalled: ''The boys in the room were like, 'There's static on that, can we check that call line? It's fuzzy.' And Mila and Kathryn were like, 'She's fine. Let's just keep rehearsing.' They were covering for me.''