Hef and Crystal celebrate their first anniversary of being together.

Hef takes the girls on an overseas trip to England and France.

Hef and the girls continue their European tour by visiting Italy and Germany.

The twins and Crystal camp in the backyard at the mansion with some friends, but end up in Hef's room to watch a movie.

Crystal, Karissa and Kristina get into trouble on a Hollywood tour bus and fear they may be arrested.

Back in the U.S., the girls arrange a baby shower for one of the Playboy Playmates.

A film shoot for a video game takes place at the mansion. Also: Crystal takes singing lessons.

Before the special Playmate of the Year luncheon, Holly decides to have a slumber party.

Hef attends a music festival in Italy and takes the twins and Crystal along to share the fun.

Karissa and Kristina prepare for roles as sexy twins in Sofia Coppola's movie "Somewhere." Meanwhile, Crystal learns she will be a Playmate and poses for her photo shoot.

Holly, Bridget, Crystal and the twins throw a baby shower for Kendra.

Hef celebrates his 80th birthday with a big celebration with his closest friends and playmates.

Bridget Marquardt hosts a fashion show to benefit an animal charity and gets Crystal and the twins to help out.

The girls and some close friends travel to Las Vegas to celebrate Kendra's 21st birthday. In true VIP fashion, they stay in luxury suite in the Palms, and Kendra finally gets an opportunity to show off her blinged-out grill.

The girls appear on the Loveline radio show with Dr. Drew, and Holly and Hef celebrate their 5 year anniversary.

The sixth season begins with Hef's new girlfriends Crystal Harris and twins Karissa and Kristina Shannon. The sisters travel to Las Vegas to celebrate their double Playmate issue.

The girls interview new candidates for bunny girls to work at the new Playboy Club in Las Vegas.

When two aspiring Playmates arrive at the Mansion to stay the night before they shoot test pictorials, Hef's girls greet them with varying degrees of hospitality. Hef makes a surprise announcement to Holly, Bridget and Kendra.

It's Halloween at the Playboy Mansion! While Holly and Kendra put their wits together to decorate tombstones, Bridget sets out on a full-scale ghost hunt and contacts a paranormal investigator to get to the bottom of the Mansion's long-running history of spirits.

"Body by Jake" taps the girls to do a workout video and the girls' planning, preparation and performances definitely get their heart rates elevated.

Hef and Crystal go to Las Vegas to join the twins. Later, they go to see Holly in a live show.

It is time for Bridget's favorite holiday Halloween, and the girls celebrate in style.

Hef and the girls visit Las Vegas for the grand opening party of a new Playboy Club at the Palms Casino Resort, and the girls sign autographs at the Playboy Store there.

When you're one of Hef's girls, your birthday party isn't just a quaint gathering, it's an event. Kendra's 20th is a two-day celebration, which starts off with a trip to the 2005 Playboy Jazz Festival with the gang and her gorgeous pal Destiny.

It\'s Holly\'s big chance to serve as apprentice editor under the tutelage of Playboy\'s west coast editor, Marilyn Grabowski.