The events of 9/11 occurred during season 2 and was the only time house guests (the final 3) were informed of outside information. This was due to one player having direct ties to the event.
Julie Chen Moonves has been the host of the American version of Big Brother since its debut in 2000. During the first season, she was widely criticized in the media for her heavily scripted, wooden delivery in her interaction with the studio audience and in the interviews on the live programs. This has earned her the nickname the "Chenbot" among the fans, a title she has proudly come to embrace.
Fans eventually became aware of the location of the house and began flying banners across the backyard for house guests. Although house guests are instructed to immediately go inside if one flies by many have been seen/read and even made impacts in the game. Most notably in seasons 2 and 8 where banners were flown during live endurance competitions where house guests could not leave the backyard.
Controversy sparked over the finale of Big Brother 3 where contestant Danielle lost to winner Lisa due to all of the evicted house guests being able to go home and watch all of the show, including diary room sessions which ultimately led to her losing by a vote of 9 to 1. This seems to be the influence for evicted house guests having to be sequestered without seeing any private footage of the show before casting to their vote, known as the jury of seven that has been in the show since.
Will Kirby stated on the live feeds during season 7 that the producers warned the Big Brother 2 house guests not to talk about the original first season that had premiered a year earlier and performed poorly. Season one was not referenced or recognized like the other previous seasons until All-Stars six years later.