The template is just "Roses are red ..." but you might be referring to the more general term "snow clone"Source: https://knowyourmeme.com/memes/roses-are-red-violets-are-blue
Ohh I remember now, on Reddit it was called "boot too big" and there was a whole sub devoted to finding images that could be paired with a roses are red poem to make a joke.
She is, without a doubt, the worst pirate I've ever heard of.
But you have heard of her...