The rat pup is fine. I have a Royal python here taking 1 small rat every 2 weeks and they are much bigger than her head. They leave a slight bulge in her which is fine. Royals should never see a mouse in their lives. They are big enough when hatched to start off on rats.
CyberGhost, I don't know where you saw it, or who said it. But it is called the Girth Rule, not the Head Rule. Trust me, if you fed using prey no larger than the head, they would starve to death.
Just keep walking and ignore the monkeys...