The puffins are a trio of unnamed female birds who auditioned to be part of Buster Moon's singing competition in Sing. In their audition, they sang the 1958 song "Lollipop" by The Chordettes.
All three of the puffins look identical, but each of them wears a different dress. The first one wears a yellow dress, the second wears a green dress, and the third wears a pink dress, all with matching hair bows and shoes.
Not much is shown about their personality as they only sang their audition in Sing.
They are seen only briefly, auditioning. Only one of them is focused enough to actually sing, albeit having trouble reaching the microphone.
Later in the film, they are seen waiting for the results of the auditions.
In the end of the film, they are seen attending the performance and the Moon Theater's grand reopening.