Mosugaba truly wants to live in peace. It is only attacking to set us free. But we can sing to Mosugaba to calm him down.”
— Island Sisters • Kirby: Right Back at Ya!
The Island Sisters (Twin Nuts in Japan) lived a peaceful existence on the South Sea Island, a tropical island located in the South Seas, singing to keep the Mosugaba caterpillar content, until one day dark clouds appeared and they were both captured by Nightmare Enterprises in the episode Caterpillar Thriller. King Dedede ordered them up, telling them to sing for him to summon Mosugaba, and, indeed, Mosugaba came to Dream Land - intent on rescuing them. While Kirby and Mosugaba fought, Tiff and Tuff found the Island Sisters locked up in a cage within Dedede's room and freed them, and had them sing for Mosugaba, which calmed him down. Thanking Kirby and his friends for their help, the Island Sisters returned home with Mosugaba.
The Island Sisters share the same physical appearance with one another. They are tiny, tan-skinned women with light blue hair and sparkly eyes, wearing only round yellow hula skirts and torn yellow tube tops, green shoes, orange earrings, and pink flower buds on their heads, and nothing else.
The Island Sisters are based on the tiny twin sisters called 'Shobijin' in the Mothra franchise. In the Japanese version, they are called the "Twin Nuts" because the actresses in that movie were also a very popular singing group in Japan called 'The Peanuts.'
The Island Sisters later made cameo appearances in the episode "Tooned Out" as model figurines as well as pictures printed on magazine covers, both of which can be seen while the Otakings are busy making their cartoon within Dedede's dungeon.
Like many stereotypical twins, they often share their sentences by either speaking in unison or finishing each other's lines.
In the Japanese version, the Island Sisters' song contains a number of hidden references to both Nintendo and HAL Laboratory in its lyrics. In the English dub, it is instrumental and instead consists mostly of soprano singing that bears resemblance to the Flower Duet, composed by Léo Delibes as part of the 1883 French opera Lakmé.