This is a fanmade duet. The big one is a lot like the hot pink singamajig but her ears mirror each other and she has heart eyes, a blue nose and a green mouth and and the little one is the exact same is the baby from the Purple duet, but he's purple with purple heart eyes, a green nose and a mouth being the same as the hot pink one's fur. This duet sings "A Sailor Went To Sea." They harmonize much like the Sea Green duet.
Here are their voices and how they sign on, enter song mode and sign off:
Sign on: Both: "Ahoy!" (1 at a time)
Song mode: Both: Sea Shanty! (1 at a time)
Sign off: Little One: Bon Voyage! Big one: Bon Voyage! Little one: Don't forget to write!
Voices: Big one: Mermaid Little one: Tangerine (While harmonizing the same pitch as the Birthday soprano)