The relentlessness of "Big Brother" begins Wednesday night, when CBS starts airing three hours of the show a week, and the live feeds start broadcasting 24/7. That triggers a cacophony of tweets, message board posts, blog posts, and sometimes news headlines, depending upon what's happening in the house.

This season's twist is that there are going to be weekly twists, delivered by special guests, which probably means at least a few former "Big Brother" cast members and actors on CBS shows the network wants to cross-promote. And it probably also means a lot of what we've come to expect, from the Zingbot to double-evictions.

But before the first episode airs, a lot has happened behind the scenes, especially during casting, when the contestants are interviewed repeatedly and told to work on their bodies for television (yes, they are!). And once you step into the soundstage that's used as a house, there's a lot more going on behind the scenes than you might know, even if you watch the feeds.

The drama and conflict is primed early
Before they even arrive at casting, the potential houseguests receive a letter with instructions for what to pack and what to expect (read the full letter). Among the things it says is to "Think about the types of people that fire you up, make you mad, bother you, etc." The letter insists "YOU DON'T" get along with everyone.

In other words, producers want them coming to casting with a strong point of view--and a strong sense of who they'll fight with in the house so the producers can cast for conflict and guarantee some good television.

"Big Brother" cast members are told to look hot
The cast often spends a large part of the summer in bathing suits and/or shirtless, and the producers are well-aware of this. They actually tell the cast members that they "should be looking and feeling your best for pool time if you make the show."

"Big Brother" finalists go through pretty much the same process as "Survivor" and "Amazing Race" contestants
A few years ago, someone who'd been through the "Big Brother" finals casting process told me all about it. It's pretty similar to what contestants on the other two major CBS reality shows, "Survivor" and "The Amazing Race," go through: being sequestered in a hotel, taking tests, being examined by doctors, and being challenged by producers and network executives.

The contestants are allowed to have contact with the outside world via the television, Internet, and phone calls, but cannot talk to one another. They can be sent home at any minute if producers decide they're not working out, and often, contestants know who's competing for the same spot on the season, if they notice someone who looks like them in the restaurant or in the gym.

Watching a previous season of "Big Brother" is a requirement
Also in the letter, potential houseguests are told that they "MUST have seen one FULL season" (emphasis is in the original letter). They're told to get them on iTunes or watch online somewhere, because they need knowledge of the game. This may explain why some non-fan players have a really limited idea of how the game can be played, or which contestants' game play they liked.

Houseguests are tested for STDs
The contract says they agree to be tested, and as we learned last fall, that actually changed one houseguest's life: "Evel Dick" Donato left season 13 mysteriously, but he explained why last fall: He tested positive for HIV. Producers told him and he left the game. Dick told me that he was given "no choice," but CBS insisted that "he was not forced to leave the show once he was informed of the positive test."

The hamsters' salary is about $37,500 a year, if they stayed in the house for a year
The "Big Brother" contract says that the houseguests receive $750 per week that they're in the game and, if they make it that far, on the jury. The two finalists — who receive either $500,000 or $50,000 — do not receive the stipend.

The "Big Brother" house is gross
A few years ago, during season 12, several TV critics and I were able to tour the house while the show was being filmed. It's a soundstage on the CBS Radford lot, as many fans now know. The most striking thing is what a gross mess it was, with the smell of trash and food in the kitchen. There was hair in the drain and, thanks to Rachel, hair extensions exposed in a bag on the floor.

That doesn't seem to be a one-time thing, since feed-watchers regularly note how the cast has to clean up before the live shows on Thursdays, and also look forward to seeing the return of ants that eat spilled food. A crew member told us that, by the end of the season, it smells really terrible

There are cameras and people on the roof, and cameras follow a track
Normally, the "Big Brother" cast can't see the camera operators or crew, since they're behind one-way mirrors in a dark tunnel called the "camera cross." Those cameras are actually on a track that goes all the way around the rooms and into the back yard, so the camera operators can move the cameras quickly and easily throughout the space.

When the contestants in the back yard, especially for a challenge, they can see camera operators and other crew members on the roof surrounding the yard. That's where there's a camera on a large jib that swoops down to capture the challenges or other action. Here's a behind-the-scenes tour of the backyard.

It's not just the feedwatchers who type everything the houseguests say
In the master control room, which is upstairs and inaccessible to the houseguests (of course), several loggers keep real-time records of everything the houseguests say and do, along with the kinds of shots that camera operators are getting. That's used later during editing to call up specific footage.

Music is played as the contestants enter the backyard for a competition
The house's loudspeakers can be used to communicate with the houseguests as a group or to give instructions to one person (such as to go to the Diary Room). They're also used to play music that we never hear on TV, but which is used to get the contestants super-excited before they compete in a challenge.

Updated on June 24, 2015 at 11:28 a.m. ET: This post has been updated to state the correct value of the prize money "Big Brother" finalists receive.