Niki and Sunwoo Playing Basketball and Table Tennis

In the Korean comments

One comment reads, in translation, “막내는 막내다..퓨마의 얼굴을 하고 있어도 너무 귀엽네” (“The youngest is still the youngest... Even with a puma’s face, he’s so cute”). The striking detail is the contrast between Ni-ki’s puma-like appearance and the cuteness the commenter still associates with the group’s youngest member.

What the words mean

“떠누” (tteonu, a cutesy form of Sunoo) has no separate literal meaning here. It is an affectionate, baby-talk-style rendering of “선우” (Sunoo), used in a comment saying he is cute.