I'm high, but imagine a zombie apocalypse au where you and some other z-team members are survivors with your own camp/base and Waterboy is a zombie.
You can't seem to shoot waterboy while you find him turned into a zombie, but he doesn't attack you because he for some reason remembers you. He doesn't remember much else, but you he remembers.
He jumps you but only to hug you. Eventually you realize he won't hurt anyone so you bring him back to camp.
The others are freaked out, but you prove that he's not dangerous by putting your hand in his mouth. He just licks and sucks on your fingers. No one trusts him, but they'll let you keep him if you keep him muzzled, in a makeshift straight jacket (a shirt where they sewn on extra long sleeves to tie back), and on multiple leashes (harness leash, collar leash, and one on the muzzle).
He freaks out if you're not around, which scares the others, but he does make a pretty good guard dog if he thinks you in danger.
His frontal lobe is a little damaged from being a zombie, so he's not as anxious anymore and just lets water fall from his mouth freely. Also due to his lack of frontal lobe function, even if you weren't together before the apocalypse, he shows you all the affection he wants, something he was too scared to do before. He constantly wants to hold you, which he will when he's not fully restrained, or he will nuzzle his head into you.
these are just some thoughts.
