Big Brother 27's first big fight hits the live feeds the night before the first eviction with one houseguest going for Rachel Reilly in a true brawl.

It was in the year 2000 that Julie Chen Moonves made her debut as the host of the hit CBS reality show Big Brother, which places a handful of strangers in isolation as they compete for a chance to take home a hefty prize.

"Big Brother" Season 27 contestants better grab a life vest, because star Rachel Reilly is checking in as the 17th houseguest

This week in the Big Brother house, Jimmy’s move to try to get Keanu ousted more than blew up in his face. Despite the exhaustive (and very shady) work he put in, when Thursday’s live eviction episode begins,

In announcing the “Summer of Mystery” theme, CBS teased that Big Brother 27 would introduce a surprise “Mystery Houseguest” as a 17th player this season. Throughout the week, the Big Brother Instagram account has sent a variety of cryptic clues through various photos of the house.

Before the season 27 premiere, many fans speculated that the mystery houseguest could be anyone from Celebrity Big Brother UK star JoJo Siwa to a Big Brother newcomer like Tom Sandoval from Vanderpump Rules. Viewers even hypothesized that this season, the host herself, Julie Chen Moonves, would join the cast as a contestant.

F loaters, grab a life vest! Rachel Reilly made her triumphant return to Big Brother during Thursday's Season 27 premiere. Now, we'll see whether she slides her way into a powerhouse alliance or winds up as public enemy number one.

"Big Brother" revealed its mystery houseguest for season 27 Thursday: the legendary Rachel Reilly. Reilly entered the house to meet the other 16 houseguests during the end of the premiere episode July 10, as she ultimately told them she was staying and competing with them this summer.

Rachel Reilly, winner of Big Brother 13, was unveiled as the "mystery houseguest" competing again this summer on season 27.CBS had been teasing a secret player all week and dropping clues on social media as to who it was.

Big Brother 27 mystery houseguest Rachel Reilly is married to Brendon Villegas. They have two children - daughter Adora Borealis Villegas and son Adler Mateo.