Holly Allen from Big Brother 21 celebrates Sunday with a barely-there bikini Sun Jul 18, 2021 at 7:54pm ET Holly Allen played on Big Brother 21 during the summer of 2019. Pic credit: CBS Big Brother 21 runner-up Holly Allen celebrated Sunday in the mountains with a bikini that had quite a few former houseguests commenting about it. A lot of members of the BB21 cast remain friends and it was fun for fans to see them spending time together in New York and New Jersey as they watched the opening to the new season of the show. Get our Big Brother newsletter! Quite a few of those same people stopped by to leave positive comments on Holly’s latest Instagram share as well.