Big Brother season 27 premiered on July 10 with a 90-minute episode. During the premiere, season 13 winner Rachel Reilly was unmasked as the "mystery Houseguest" who would be joining the contestants in Hotel Mystère. In July 2025, Chen Moonves told Entertainment Weekly that "people should be afraid of [Reilly] and of getting in her crosshairs."

Lauren Domingue, a Lafayette native, was evicted from the CBS Big Brother House with 9-5 votes, but is still doing well in the game, making alliances and making friends.