04/10/2011 at 12:25 PM EDT
Karina Smirnoff says she posed for Playboy
to test her limits
. But Hugh Hefner's reason for having the Dancing with the Stars
pro pose is more clear cut.
"I think it's obvious," Hefner told PEOPLE at his 85th birthday party at Las Vegas's Palms Casino Resort on Saturday. "She has a very good following from the show and the pictorial is unforgettable."
head honcho wasn't at Smirnoff's photo shoot
but has certainly seen the spread. The pictures, in which Smirnoff wears little more than a few red ribbons, incorporates her dancing, as well.
"It's a beautiful shoot and I'm very proud of it," added Hefner.
When asked what is sexy, Smirnoff told Playboy
, "Sexy is the comfortable feeling of being who you are."