Heigl's flirting shame with gay co-star Knight

Katherine Heigl was shocked to find out her co-star and friend T.R Knight was gay - because she had spent the show's pilot flirting with him.

The 'Knocked Up' beauty was single when shooting began on the hit US show - and 35-year-old hunk Knight caught her eye.

But the actress' romantic plans didn't make result in any romantic liaisons - because her lustful looks were ignored as Knight is gay.

She says: "When we were filming the pilot I was single and so was he and I kind of had my eye on him. I was getting nowhere and I was super-confused.

"I was like, 'Hello? Do I have something hanging out of my nose? Why aren't you paying any attention to me? Needless to say, it quickly became a friendship once he told me."