Big Brother season 27 debuts tonight, and there’s a mystery houseguest joining the ranks.

If you don’t know, there won’t be a live move-in this year for the CBS reality TV show. Instead, the first episode has been seemingly pre-taped.

Meaning…the mystery house guest has already been revealed to the new contestants.

The Big Brother social media pages have been dropping hints and clues about who this person is, and we’ve gathered some of the biggest guesses.

Keep reading to find out more…

Host Julie Chen Moonves told EW, “What I can say is the mystery houseguest, when I was told who this person is, I had to expect the unexpected! I never expected that person. And I was very excited because, in my opinion, getting that person is epic. And that person is also very polarizing. So there’s going to be a strong reaction in both directions for this mystery houseguest.”

Guess number one: Former BB winner Rachel Reilly.

Former BB contestant Janelle Pierzina really got this rumor up and running after she tweeted that she couldn’t get in touch with Rachel. This is a sign that Rachel could have been in sequester with the other BB contestants for the 27th season. You see, before contestants join the house, they are placed in sequester leading up to competing. They don’t have their phones, so this would make sense if someone was not responding.

However, Janelle eventually confirmed she had heard back from Rachel, posting on X, “Rachel text me back! She’s not sequestered and she’s enjoying her Sunday in Birmingham. #BB27″

Guess number two: BB26 contestant Angela Murray.

Fans have thought it could be her due, as she definitely made an impact in season 26. There’s no hard proof that it is her, apart from fans noticing her Cameo videos stopped over July 4 weekend.

Guess number three: Cody Calafiore or Derek Xiao

Past BB fan faves Cody or Derek have been guessed. Why? Big Brother released a mystery portrait that fans think might look like either Cody or Derek.

Guess number four: BB17 contestant Vanessa Rousso

One eagle-eyed fan tried to put some clues together and guessed BB17 contestant Vanessa Rousso.

They tweeted, “I like the new theory that the mystery houseguest is Vanessa Rousso, let’s run with that. BB posted “secret 17″ and their latest photo has a card under a hat.. Vanessa, poker player, #bb17 #bb27″

Tune in to BB tonight to catch all the drama unfold! And, see the new houseguests here.