She was a X girl and he was a Y boy refers to a series of memes originated from an image of Jesse Pinkman (Aaron Paul) and Jane Margolis (Krysten Ritter) from the popular TV show Breaking Bad.

Example :
She was a X girl and he was a Y boy refers to a series of memes originated from an image of Jesse Pinkman (Aaron Paul) and Jane Margolis (Krysten Ritter) from the popular TV show Breaking Bad.
Example :