After Treader is put to sleep, Duff decided to become Izzy's pet.
"Of course!" The blond grinned, resting his head on Izzy's lap and leaning into his touch, closing his eyes. "I think I need a new collar."
"You're asking too much, Duffy." Izzy leaned down, pecking his lips softly. "You're not a dog, Duffy. Even if you do bark well, I prefer you as human."
"But I'm still your pet, and I need a new collar. And then we can buy more dog biscuits~!" Duff chuckled, it wasn't his fault if they were good! Also, he was used to wearing a collar, and he and Izzy did agree that he'd be his pet for all eternity. They just had to hide that from the press and the fans.
"Later, then…" The dark haired smiled, they always ended up in this argument for one thing or another, but it was a strange thing even now. It started after Izzy lost his dog, he had to be put to sleep, and Duff wanted to cheer him up… so he'd attached a leash to the chain around his neck, put on false dog ears and tail, and tied a red present bow around himself, sleeping by the side of Izzy's bed and waiting for the smaller man to wake up and find his 'present'.
Then, Izzy found out he liked dog biscuits, and was practically forced to have Duff as his pet, because or else the blond would go out to live on the streets with other ownerless dogs… or at least he said so. In the end, it was just strange, but he was getting used to having his boyfriend be his pet, just as long as Duff didn't insist on being a dog, but maintained what came to be his 'normal' pet self.