The 41-year-old recently announced that he is expecting a baby with model Lara Stone, who he married in May 2010.
The Little Britain star said that the closest he has come to tasting breast milk is through his character Harvey Pincher - a grown man who is still breast fed.
Speaking on Alan Carr's Chatty Man, Walliams said: "I was never breast-fed, apart from on the show. With my mum it was formula. I have always wanted to taste breast milk, as I've heard that it's sweet and salty at the same time."
The Britain's Got Talent judge also admitted that he had wanted to start a family soon, after worrying that he would be mistaken for a grandfather.
"We were just thinking about it now I'm married and I'm quite old. I'm 41, so I thought I'd better get on with it. You start thinking, 'When they're 18, I'll be 60'. I'll be at the school gates and people will be asking them, 'Is that your granddad?'"
Stone recently showed off her growing bump at an event this week, and Walliams admitted that he found her more attractive pregnant.
He said: "She looks so full of life and happy, it's great."