Play video content CBS

"Big Brother" houseguest Kaitlyn went from zero to stupid real quick when she dropped the n-word Thursday night during the show's online live feed.

She was talking to 2 other guests -- Tyler and Scottie -- about making a quick transition ... when Kaitlyn, who is white, decided it was the perfect time to quote Drake's "0 to 100" ... and NOT the clean version. She said, "I did go zero to 100 n**ga, real quick."

Seems like she realized her idiocy real quick too ... because she immediately said "Oops," and continued mumbling lyrics to the song as if to say ... I was just singing a song, I'm not racist!

Play video content CBS

All 3 of 'em must have remembered at that moment producers JUST finished warning them about this kinda crap ... after Angela and Rachel worried their tans would make them look too "ghetto."