Socialite Kim Kardashian says rapper-fiance Kanye West's marriage proposal was the "surprise of a lifetime".

The `Stronger` hitmaker asked the brunette beauty to be his wife in front of all her loved ones at AT&T Park in San Francisco on her 33rd birthday and Kim, who has eight-month-old daughter North with Kanye, later admitted she had no idea what was going to happen.

"I'm, like, shaking. It is so crazy to me that this is all happening. Kanye really outdid himself. It feels like I'm in a dream. It's just the most amazing experience. I am the biggest investigator, so the fact that I didn't see one sign of this happening is the surprise of a lifetime,` contactmusic.com quoted Kim as saying.