Jennifer Lawrence almost ''lost consciousness'' when Kris Jenner made a surprise appearance at her birthday party.

The 'Hunger Games' is a huge fan of 'Keeping Up With the Kardashians' and couldn't believe it when the 59-year-old matriarch turned up to her recent 25th birthday celebrations.

She told The New York Times newspaper: ''My knees buckled. I fell. Seriously! It was the closest I've ever come to losing consciousness. I had NO IDEA. I'd never met her before, but we've always watched 'Keeping Up With the Kardashians'.''

Kris shared a picture of herself and Jennifer in bed on her Instagram account at the weekend, in which she referred to the 'Silver Linings Playbook' star - who turned 25 on August 15 - as ''a piece of s**t'', which the actress explained was in reference to her birthday cake, which the reality star was tasked with bringing into the room.

Jennifer said: ''My two best friends planned a surprise birthday party with a big surprise within the surprise. So, I'm there, and people start singing 'Happy Birthday.' Kris Jenner comes out holding my cake, which is a pile of sh*t, with a sign that says 'Happy Birthday You Pile of Sh*t'.''

And the 'X-Men: Apocalypse' star particularly enjoyed doing karaoke with her idol.

She added: ''Kris Jenner and I sang 'Build Me Up Buttercup' on karaoke and took that picture.''