(Agencies)
Updated: 2008-01-31 14:00

In this image released by Playboy Enterprises,
the cover of Playboy's March 2008 issue,
featuring, 'The Girls Next Door's'
Kendra Wilkinson, left, Holly Madison, center,
and Bridget Marquardt, is shown. [Agencies]

Three is the magic number for Playboy magazine's March issue. Holly Madison, Bridget Marquardt and Kendra Wilkinson-better known as Hugh Hefner's trio of blonde girlfriends from E!'s "The Girls Next Door" reality series -will appear for the third time on the cover of Playboy.

"It kinda happened by accident," Hefner told The Associated Press. "It was not the original plan. I knew we were overdue for a cover featuring the girls. For our annual sexiest celebrities list, we always get votes from readers on the Internet of who should be on the top of the list. Lo and behold, as the votes were coming in, we found the girls moving up higher and higher on the list."

Madison, Marquardt and Wilkinson will be featured together in three different covers for the "25 Sexiest Celebrities" issue. In the newsstand edition cover image, out Feb. 8, the women are clad in glittery lingerie in front of a starry backdrop.

"To be perfectly frank, I have unexpectedly fallen in love," Hefner said of his ongoing relationship with the three women. "It is the relationship with Holly that will probably last forever. The others will last for as long as they want it to last before going on with their careers and lives."

Among the celebrities to make Playboy's list are Jennifer Love Hewitt, Alicia Keys, Cameron Diaz, Beyonce, Christina Aguilera and Britney Spears. Hefner said the top three online celebrity vote-getters were Angelina Jolie, Scarlett Johansson and Jessica Alba, with "The Girls Next Door" coming in fourth place.

"Yes, there was some favoritism involved," Hefner joked. "I know them personally."