merupo

めるぽ.
A meme associated with Merlin Prismriver. It's a pun on "Nurupo" [ぬるぽ], another 2ch computer-programming meme short for Null Point Excpetion (Used in the same way as "Disregard that, I suck dicks" would.).
It comes from the fact that due to a bug in Perfect Cherry Blossom, Merlin would act improperly during the Prismriver's final spell card. This cause fans to portray her as crazy or rebellious.
For the purposes of the tag, it has to do with Merupo's Shift-JIS: ξ・∀・） in the picture, sometimes replacing her face.