• Though not really a rule, twelve contestants appeared on Big Brother 2, opposed to ten on Big Brother 1.

• The HouseGuests no longer gave nominations that were voted on by the public. Instead, they competed to become Head of Household (HoH). The winner of this position was given a separate bedroom and the right to nominate two HouseGuests for eviction.

• The ultimate winner of the show was determined by a vote of the ousted HouseGuests rather than the public. During this season only, however, all ousted members of the house, became voting members of the jury while in future season only those HouseGuests who lasted until the final weeks became jury members. Justin Sebik, who was expelled, did not return for the finale and did not play a part in the final vote.

• In a special twist this season, the two remaining HouseGuests got to decide which HouseGuest's vote they could void, in hopes that their vote was for their opponent, and that they would gain an advantage over the other player.

• During this season, the food competitions were introduced. HouseGuests competed against each other for the right to win food, and the losers were put on a diet of only Peanut Butter and Jelly for all their meals for the week. The Peanut Butter and Jelly punishment diet lasted through until Season 7 when it was replaced with the "Slop" punishment diet.

• This season marked the end of the free internet feeds that the public had access to during the show's first season, and CBS introduced a paid user fee system.

• The house itself was renovated, and evicted HouseGuests did not exit into the outside world as in season one, but instead exited into a closed studio where they were interviewed by Julie Chen. After their interview with Julie they would meet up with family members or friends in a feature that was dropped in later seasons.

Memorable events

• About two weeks before the end of the second season, the September 11 attacks pre-empted television for an entire week. In a move away from the rule of not letting the houseguests in on information from the outside world, the three remaining houseguests were told of the news. Contestant Monica was told, in the diary room by executive producer Allison Grodner that her cousin Tamitha was presumed missing at the World Trade Center. The week after the attacks, the game continued as normal.

• In week two houseguest Justin Sebik placed a knife to the throat of fellow houseguest Krista, asking "Would you get mad if I killed you?" Both competitors were under the influence of alcohol, but Justin was disqualified from the show and evicted immediately. The houseguests were notified the following morning via the voice of executive producer Arnold Shapiro, who asked them to gather up Justin's belongings to be sent home.

• The first true strategic alliance of any Big Brother season was formed when contestants Mike and Will formed the "Chilltown" alliance, which was later joined by Shannon and Krista.

• Volatile houseguest Shannon became known for her temper. In one memorable moment, she was chastised by the producers when she angrily scrubbed the toilet with the toothbrush of houseguest Hardy, after they had had a fight. In another encounter, she placed a bag of potato chips on houseguest Autumn's pillow to insinuate that she was fat.

• The houseguests received a short visit from some contestants of the other CBS reality show Survivor. Gervase Peterson and Susan Hawk from Survivor: Borneo and Alicia Calaway and Jeff Varner from Survivor: The Australian Outback visited the house for a few hours in an episode that aired on September 5.

• On finale night, the audience was updated that former houseguest Sheryl was diagnosed with breast cancer and needed to undergo chemotherapy, as well as the news that Monica's cousin Tamitha had died at the World Trade Center.

• During the show's final episode, contestant Mike "Boogie" proposed marriage to fellow contestant Krista, with whom he had a romance on the show. They would later break up.