"Shipoopi" is the title of a song from The Music Man, a Broadway musical written by Meredith Willson.
"Shipoopi" is also a portmanteau of the words "shit" and "poopie"; which is perhaps why children enjoy performing the "Shipoopi" song in Willson's musical.
lyrics from "Shipoopi":
Now a woman who'll kiss on a very 1st date,
Is usually a hussy,
And a woman who'll kiss on the second time out,
Is anything but fussy,
But a woman who'll wait 'till the 3rd time around,
Head in the clouds, feet on the ground,
She's the girl he's glad he's found,
She's his Shipoopi.