Season 18 of Big Brother kicks off tonight. The way the beloved reality show usually works is that a dozen contestants live in a large house, where they're cut off from their friends, family, and the rest of the world for at least three months in an attempt to win $500,000. It's been on the air since 2000, premiering the same summer CBS first ran Survivor. Despite, or because of, some controversial moments and a shaky beginning, the show continues to attract viewers three times a week on television, and voyeurs who watch a 24/7 live feed of the house and its inhabitants online. But first ... 

1. IT BEGAN AS A DUTCH SHOW.

John de Mol—who also created The Voice—created Big Brother for his TV production company, Endemol Entertainment, in 1997. The show began its run in 1999, in the Netherlands. When asked about his creation, de Mol said, "There is a bit of a voyeur in each of us ... You learn more about life from watching Big Brother than from reading a book."

2. ONCE CONTESTANTS PASS THE AUDITION PROCESS, THEY ARE IMMEDIATELY—AND CONSTANTLY—SUPERVISED.

Former participants have said they were at times only given 60 to 90 minutes to pack a suitcase. Those that need to take a flight out to Los Angeles are not allowed to talk to anyone on the plane, and a handler is there to ensure he or she doesn't break the rules. Their IDs and wallets are taken once at the hotel. Some contestants have been able to read magazines and books at the hotel while some have not. They're given old episodes of the show to watch to prepare themselves.

3. THE FORMAT HAD TO BE CHANGED AFTER THE FIRST SEASON.

Like the Netherlands version, in season one of America's Big Brother, viewers were responsible for voting out contestants every week. Recognizing that having the viewers in charge of the voting made the contestants act too ethically, executive producer Allison Grodner changed the rules so that, beginning in season two, the eviction power went to the houseguests, giving each of the contestants a "survival of the most manipulative" mentality.

4. CONTESTANTS AREN'T TOLD OF OUTSIDE EVENTS. BUT THEY MADE AN EXCEPTION IN 2001.

During season two, the final three Big Brother contestants were informed of the September 11th terrorist attacks. One of them, Monica Bailey, lost a cousin. Bailey opted not to talk to her sister, nor did she leave the show.

Other than that, contestants are told little to nothing. Season four player Erika Landin told The Huffington Post that the limo driver taking her from the house to the airport so she could finally go home said, “You’re never going to guess who our governor is: Arnold Schwarzenegger.” She replied, “Oh please, really? I know I’ve been away for a little while, but Arnold Schwarzenegger is the governor?”

5. THERE IS A TOTAL MEDIA BLACKOUT.

Big Brother contestants are not allowed access to television, radio, phones, or the internet. They're not even allowed to have writing utensils or paper. They can, however, play chess. And the only book allowed inside the house is the Holy Bible.

6. FANS HAVE FLOWN BANNERS OVER THE HOUSE.

Whenever this occurs, the houseguests are immediately instructed to go back inside (though producers are not always successful.) Producers have sent cease and desist letters to aerial advertisers to get them to stop potentially revealing twists to the game to contestants.

7. CONTESTANTS ARE NOT ALLOWED TO SING, OR QUOTE MOVIES.

Singing or quoting movies is not allowed for copyright reasons. If a contestant does do this, the 24/7 live feed cuts out momentarily, while a producer—usually co-executive producer Don Wollman—issues a warning. Houseguests are also not allowed to talk about the production of the show itself, nor about what they said in the Diary Room, as that is only intended for the contestants to inform the CBS audience of what they were thinking and feeling.

8. SOME HOUSEGUESTS HAVE BEEN EXPELLED.

Justin Sebik pulled a knife on Krista Stegall in season two. Stegall said the producers "blew that completely out of proportion" and said she had no memory of Sebik holding a knife, but later sued CBS over the incident. Scott Weintraub was forced to leave during season four for throwing furniture. Chima Simone was forced to leave during season 11 when she refused direct orders to put a microphone on, then tossed a microphone into a whirlpool spa when another contestant handed her one. Simone later said she felt the game was fixed. Willie Hantz was expelled in season 14 for head-butting housemate Joe Arvin.

9. SOME PLAYERS HAVE LEFT VOLUNTARILY.

Neil Garcia left on day seven of the ninth installment of the show due to a personal matter. Paola Aviles left while she was sequestered right before season 12 was to start. Dick Donato, who had won the eighth season of Big Brother, was competing again on season 13 when producers informed him a blood test revealed he was HIV positive, leading him to leave the show.

10. THE FOOD RESTRICTION WAS CHANGED FROM PEANUT BUTTER AND JELLY TO "SLOP."

Sometimes the punishment given for losing a challenge is to be put on a slop-only diet for a period of time. Prior to season seven, it was a PB&J-exclusive diet. The slop resembles oatmeal, and has been described as "one part 'slop mix' and one part water." The hypoglycemic season nine contestant Amanda Hansen was rushed to the hospital after suffering a seizure due to a lack of sugar from just eating the slop, though she eventually returned to the house. Similarly, Hansen's fellow season nine housemate Allison Nichols also had an allergic reaction to the mysterious mixture, was also hospitalized, and also returned.

11. CONTESTANTS DON'T ALWAYS GET A LOT OF SLEEP, UNLESS THEY MAKE IT TO THE END.

"They blare pop songs in the morning to wake you up. It could be any time between 8 a.m. and 11 a.m.," Big Brother 15 winner Andy Herren revealed. "You have to wake up to change your mic pack out, and then once you do that, you can go back to bed if you want. In the early and middle stages of the game, I slept five to six hours a night, just because I was in the mindset of 'last to bed, first to wake.' During that last week, I was sleeping 15 to 18 hours a day because there would literally be nothing to do."

12. CONTESTANTS GET PAID, WHETHER THEY WIN OR NOT.

Each houseguest gets $750 for every week they are in the house or sequestered to serve on the nine-person jury that decides the winner. The second place winner, who wins $50,000, and the $500,000 grand prize don't get the stipend.

13. POTENTIAL JURORS ARE SEQUESTERED, THOUGH THAT WASN'T ALWAYS THE CASE.

In season three, evicted houseguests went home and watched the show, and saw Danielle Reyes make disparaging comments about them in her Diary Room confessionals. It was the reason for Reyes losing to Lisa Donahue by a vote of 9 to 1. After that, producers sequestered the potential jurors and did not allow them to watch the show.

14. IT WAS THE LAST PRIMETIME SHOW ON NETWORK TELEVISION TO SWITCH TO HD.

The season 16 premiere, which aired on June 25, 2014, was the first high-definition episode of Big Brother. The switch to digital took three years because a new digital post-production system needed to be built, installed, and tested. All 80 cameras had to be swapped out, and 14 miles of HD cables had to be laid down throughout the house.

15. THERE HAVE BEEN A FEW BIG BROTHER WEDDINGS.

Jeff Schroeder and Jordan Lloyd met as contestants during season 11 of the series (Jordan ended up winning.) They also competed in season 13, and while visiting the houseguests of season 16, Schroeder proposed marriage. They married in March 2016.

Dominic Briones and Daniele Donato met while filming season 13 and wed in 2013. The ring bearer was the 5-year-old son of another former contestant.

Rachel Reilly and Brendon Villegas met during season 12 and were engaged by season 13, when they both returned (Reilly won that series).