Hippo Birdie Two Ewes= Happy Birthday To You
There's an American cartoonist that was popular back in the 80's (named Boynton) that made a birthday card with all these animals on the front. When you opened it, the card said:
Hippo birdie two ewes, hippo birdie two ewes, hippo birdie deer ewe, hippo birdie two ewes (think of the birthday song)