It's wrong to defecate in other people's belongings.
Fred and James are always playing unexpected pranks on each other.
Fred wants to prank James in way that he's never done before.
Fred gives James a spring snake disguised as a can of chips.
Fred defecates in James' bag and puts it where James can find it.
James opens the can and laughs as the snake pops out.
James becomes furious with Fred for ruining his bag with feces.