Mahna Mahna: I know a couple, name of Jack and Jill.
They love each other and they always will.
'Cause when Jill gets an itch in the middle of her back,
All she does is turn to Jack.
And she says:

Jill: Scratch my back!
Oh, baby, won't you scratch my back?
Really nothing to it!
Love it when you do it!
Baby, won't you scratch my back?

Mahna Mahna: When Jack feels itchy, they just make a switch.
He turns to Jill and says:

Jack: I've got an itch!
Come on, Jilly, won't you be a peach
And scratch the itch that I can't reach?
And you can scratch my back!
Oh, honey, won't you scratch my back?
Really nothing to it!
Love it when you do it!
Honey, won't you scratch my back?

Mahna Mahna: They'll be so happy 'til the end of time,
Sayin':

Jill: I'll scratch your back if you'll scratch mine!

Jack: We're lovey-dovey as a couple can be,
'Cause I got you and you got me!

Jill: And you can scratch my back!

Jack: And, honey, you can scratch my back!

Jill: Really nothing to it!

Jack: Love it when you do it!

Jill: Baby, won't you scratch my back?

Jack: Honey, won't you scratch my back?

Jack and Jill: Love it when you scratch my back!

(During the song, Jack and Jill take turns scratching each other. But at the song's end, we see Mahna Mahna between them, scratching both backs at once!)