Okay, so you pick a song, and change the lyrics. Simple.

Example:

Orignal: Milkshake (you dont have to put the artist or whatever)

My milkshake brings all the boys to the yard,
And their like: It's better than yours,
Damn right it's better than yours,
I can teach you, but I have to charge.

Final Fantasy:

My Cure spell brings all the boys to the yard,
And they're like: "It's better than yours."
Damn right, it's better than yours!
I could Heal you, but I have to charge.

Not very good but you get the idea, so have fun!