Art by nelson and victor, thanks to them again and again. It is based on a silly joke Mommy and I had after watching Sweetie Belle in a lamb costume in season 7 episode 6 of MLP. So here it is. You just can't see Fiona's diaper here, but that the only difference with the idea I suggested.

Little Fiona Runt has lost her sheep
And doesn’t know where to find her.
Leave the lamb alone
And she'll come home
Wagging her tail behind her diaper

Little Fiona she searched for her sheep
But didn’t quite know how to find her
She looked everywhere
Crinkling from here and to there
But still couldn’t think where to find her

Little Fiona began to weep
And lay down to rest for a while
Comfy in her diaper, she fell fast asleep
While counting her sheep
Then dreamt they came home with a smile

Little Pup Fio' had fallen asleep
And dreamt that she was all alone
But when wet she awoke
And pulled back her cloak
She saw that her sheep had come home

Little Fiona Runt had lost her sheep
And didn’t know where to find her.
She left the lamb alone
And she came home
Waiting for her to change her diaper