It is a name for a persone with a high-pitched voice who always ends up in shit. This word is derived from the lovable character, Pikachu, with his high pitched voice and a turd as a person who always gets into shit.
Blond: <laughing hysterically> ah shit, my mom caught me again trying to have sex in their bed
Friend: You are such a Pika-turd, you keep on getting in the same shit. And stop laughing like a prick!