Season Twists

Big Brother 1	The premise of the show -- "America watching in on a group of people" -- is introduced.
Big Brother 2	The new format is introduced -- a Head of Household nominates two HouseGuests and the other HouseGuests vote on which nominee is evicted.
Big Brother 3	"Operation Revolving Door" -- At the beginning of Week 5, the first four evictees competed against one another, answering trivia questions until they were reduced down to two. Then, the HouseGuests, still in the house, voted on which of the two they wanted to return. ALSO, The Power of Veto is introduced, allowing HouseGuests to change the Head of Household's nominations.
Big Brother 4	"The X-Factor" -- Five of the HouseGuests are joined by their ex-boyfriends or ex-girlfriends -- Amanda and Scott, Alison and Justin, Jun and Jee, Michelle and David, Erika and Robert.
Big Brother 5	"Project DNA: Do Not Assume" - A set of identical twins secretly play as one HouseGuest, switching places intermittently in secret -- Adria and Natalie. Two other HouseGuests find out that they are related -- Jennifer "Nakomis" and Michael.
Big Brother 6	"Summer of Secrets" -- Each HouseGuest has a secret partner. If a set of partners makes it to the Final 2, the winner wins $1,000,000 and the runner up receives $250,000.
Big Brother 7-All Stars	"All Stars - A House of Extremes" -- 14 former HouseGuests get to play the game again.
Big Brother 8	"Biggest Nemesis" -- Six of the HouseGuests learn they will be playing against nemeses from their pasts - Joe and Dustin (Ex-Boyfriends), Daniele and Dick (Estranged Father and Daughter), Carol and Jessica (Ex-Best friends). One HouseGuest, Eric - known as America's Player, must perform certain tasks given by viewers of the show for financial rewards.
Big Brother 9	"Til Death Do You Part" -- Players are paired up with their "soul mate," with whom they must play the game. The soul mates will have to compete together, win Head of Household together and face eviction together. Oh, and share a bed.