우!우와와 우와☆(･ω･*)ゞ

In the Korean comments

One comment reads, in translation, “Siyeon being the only one with an ㅇㅁㅇ face is seriously so cute.” The text-face depicts wide eyes and an open mouth; another commenter gives viewers a second detail to watch for, saying that Siyeon gets the choreography wrong.

What the words mean

“커여운” (keoyeoun, cute) is a deliberately distorted form of 귀여운 (gwiyeoun, cute). It carries the same basic meaning here, but its intentionally babyish spelling makes the praise more playful and affectionate.