Big Brother unveiled the identities of the three returning houseguest "duos" and revealed the season's eight first-time houseguests will similarly initially compete as pairs during Thursday night's premiere of the CBS reality show's thirteenth season.

In addition, Big Brother host Julie Chen also revealed the season's "duos" twist will result in the season beginning with each week's Head of Household nominating one duo for eviction and the surviving duo member then receiving immunity until only 10 houseguests remain.

Afterward, all 14 houseguests also competed in the season's first Head of Household competition and crowned former twelfth-season houseguest Rachel Reilly -- who returned to the house as one of the former houseguest duos -- the thirteenth season's initial HoH.

Big Brother's thirteenth season premiere began with Julie having the season's eight first-time houseguests move into the house and select their bed assignments.  However, given there were only eight of them, the houseguests immediately began suspecting a twist was coming.

"There's like a crazy surprise!" Porsche Briggs, a 23-year-old VIP Cocktail Waitress who currently resides in Miami Beach, FL, told Shelly Moore.

"There's got to be," replied Shelley, a 41-year-old outdoors industry executive who currently resides in Prairieville, LA.

"Oh my god!" Porsche said.

"I know there's a twist somewhere because there's only eight of us in the house... I know it's not just going to be eight," Dominic Briones, a 25-year-old student from San Mateo, CA, explained in a Diary Room interview.

After they introduced themselves -- and lied about their backgrounds, in some cases -- to each other, Julie revealed the "duos" twist to the eight new houseguests and instructed them to organize themselves into pairs.

"This summer, you will be partnering and playing the game with someone in this room.  Who you choose will be up to you, but... the game has changed," she explained.

"If you win Head of Household, you and your partner will be safe for the week.  But instead of nominating two individual houseguests for eviction, you will be nominating one duo."

Keith Henderson, a 32-year-old human resources manager from Bolingbrook, IL, then immediately asked Porsche -- who he was attracted to -- to ally, and she accepted.  They were then followed by Shelly and Cassi Colvin, a 26-year-old model from Allen, TX who currently resides in Nashville, TN.
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Adam Poch, a 39-year-old music industry manager from East Brunswick, NJ, then asked Dominic to partner -- leaving Lawon Exum, a 39-year-old legal file clerk who currently resides in Inglewood, CA, and Kalia Booker, a 30-year-old writer who currently resides in Los Angeles, CA, paired together by default.

Later, Julie revealed the eight houseguests weren't "the only pairs playing the game" and the six additional returning houseguests joined the competition.

Rachel was the first returning houseguest to enter the Big Brother house and was accompanied by Brendon Villegas, her former twelfth-season "showmance" partner turned real-life fiance.

They were followed by eleventh-season Big Brother winner Jordan Lloyd, a 24-year-old receptionist from Matthews, NC who entered the house with Jeff Schroeder, a 32-year-old former salesman from Norridge, IL she began dating after their Big Brother season concluded in 2009.

Dick "Evel Dick" Donato, a 48-year-old former bar manager from Los Angeles, CA who won Big Brother's eighth season in 2007, and Danielle Donato, his estranged 25-year-old daughter were the final pair of former houseguests to join the house.

Following another round of introductions, the seven houseguest pairs then competed in the season's initial Head of Household competition.

Dubbed "Going Bananas," it required each member of a duo to hold on to giant bananas while "chocolate" and "whipped cream" was sprayed on them.  The houseguest who held on the longest would become the first HoH.

Rachel and Danielle were the last two houseguests competing and Rachel was crowned the first HoH when Danielle agreed to drop out after Rachel agreed to "swear" not to nominate Danielle or her father.

Julie then revealed the premiere's final twist -- that the surviving duo member of a duo which loses a member to eviction will receive immunity until only 10 houseguests remain -- to all the houseguests.

"I huge advantage survives the houseguest who survives the chopping block -- it's called the Big Brother Golden Key," Julie explained.

"The Golden Key guarantees you a spot in the Top 10.  Anyone who survives eviction in the first four weeks of the game can not be nominated [again] until only 10 of you remain in the house.  And because the holder of the Golden Key can not be evicted, they will not participate in any competitions during that time.  However, they will vote for eviction."

Big Brother's next episode will Sunday, July 10 at 8PM ET/PT on CBS.