Ata chooses to sing a classic Samoan kids song, Savalivali Means Go for a Walk.
The smiley mother and son duo then start singing.
"Savalivali means go for a walk, Tautalatala means too much talk. 'Ou te alofa iate 'oe means I love you, Take it easy fai fai lēmū" they sing.
The duo then performed an impromptu serenade for their host Fallon, who is thrilled.
"You just stole the interview. You're unbelievable! You are a superstar" he tells the 72 year-old.
He posted the video of them singing to Instagram saying "A career first ... singing with my mom @atajohnson on @fallontonight."
"Best part of all this is she's so happy doing this for Jimmy (whom she adores). So happy! I love it. Meanwhile I'm like "imagine if she was drunk", he wrote on Twitter.