This blog will be a survival guide on all CP monsters, I'll update often(Giving the middle finger to most of these CPM's will end up with a missing finger):
Jeff The Killer
Jeff has this twisted fantasy of making people beutiful in his own twisted image so simply when he says "Don't you want to be beutiful" simply respond "If everyone is beutiful then no one is beutiful because there is no comparision and everyone will look average. I would (And my beloved ones) to be the ones who remain ugly so that the beutiful can be beutiful). As for the "Go To Sleep" tell him that you need to play COD and that he's welcome to join.
So he's a teleporting white octopus man frankly the only way to keep yourself from this guy is do something completely random and unexpected like a wave competition or give him a hula skirt a teach him to hula. And in the worst scenario get a japanese man on the scene he'll make sushi out of that octopus.
Throughout his story he fed off the guy's fear therefore ignoring him from the start will keep him weak. Or you can simply give him swimming lessons so he won't drown.
This guy crawls on his hands and feet, the best defense is a hidden hole with spikes he falls in a hurts himself and if your really smart you made a bugspray/lighter flamethower that you use to burn him. And if you live in America just set up land mines around your house