To be soaked in pig's blood refers to the book and movie "Carrie", in which the titular character is humiliated by her classmates for the last time and goes completely fucking nuts!
Sam got soaked in pig's blood, so now she wants to burn the school down
Simalar to the "Ice Bucket Challange", accept the ice water is replaced with urine and excremiment. The challenge is often issued to someone that you don't like.
I challange Paul to the piss soakeddump bucket challenge!