Wacky comedy duo Ylvis have signed a deal to turn their unlikely hit The Fox (WHAT DOES The Fox SAY) into a children's book.

The Norwegian brothers, Vegard and Bard Ylvisaker, originally recorded the tune and made an accompanying video to prank Tv bosses, but the track has become a chart-topping sensation and the promo has racked up 213 million YouTube hits - and now the siblings are set to become authors thanks to the catchy hit.

Officials at U.S. publishing house Simon & Schuster signed the brothers to adapt their catchy lyrics into a book, titled What Does the Fox Say?

Ylvis' first book will hit shelves on 10 December (13).