I think it started with a Marisa, and back then, "Drop Dead Easy" Was their trademark shithead phrase, the same way Reimus back then had as their trademark phrase the "Pitiful Heroine" line.
Now a days, Shitheads share phrases, at least when they are like "Drop Dead Easy", since pitiful heroine is still a reimu thing, the same way we have the "Great Marisa" for the Marisas.