Actor Jason Segel was left red-faced on the set of U.s. sitcom How I Met Your Mother recently - when guest star Britney Spears blanked him after he made a joke.

Segel was bemused by the paparazzi in helicopters circling the show's Hollywood set trying to get a shot of Spears, who had a cameo role as a secretary on the TV comedy.

So the comedian approached the Toxic singer to offer an alternative explanation for the choppers in the sky - but she didn't get his joke.

Segel says, "I went up to her and said, 'I'm sorry, I have this big movie coming out - this is what it's like for me.'

"She looked at me strangely and walked away."