The Itsy Bitsy Triangle (to the tune of the Itsy Bitsy Spider)
The Itsy Bitsy Triangle, had three-e sides.
The two little sides were scared and so did hide.
But then they found out, that they could both square-up
So A squared and B squared equaled C Squared, Yup!
It's not going to win a grammy but it's got a rhyme and it includes the formula.
The best inspiration for this really comes from Bill Nye the Science Guy:
It's the same song as Sweating Bullets by Megadeath, just with the lyrics changed.
For students who are stuck I suggest they look to rap songs as well because you get away from the musical and more towards the concepts of rhyme and meter instead.