These are bloopers that get what made the original show fun in the first place: watching these absurdly serious basketball prodigies fail spectacularly at being normal humans. Episodes are short enough to slip between other shows, but they hit harder because you already know these characters, already understand the rhythm of how they interact. Kuroko actually laughing is a gift the parent series never quite allowed itself to give you.
Kuroko's Basketball Specials is a set of nine short comedy extras from 2012, made as animated bloopers for the basketball series. The shorts adapt the bonus pages that appeared in the original manga, and they were packaged with both the limited and regular BD/DVD releases of Kuroko no Basket. Instead of tense matches, they offer lighthearted outtake-style humor for fans of the main show.