The fourth one

Horny: "I'd like to chat with the fourth one."

callmeSir: "Wonderful, I'll let her know."

A moment later, callmeSir posted an invitation to a private chat room. You click it, and enter.

Horny: "Hello."

LuckyPuppy: "Hi." There is a pause before the next message.

LuckyPuppy: "May I call you Master?"

Horny: "I guess so?"

LuckyPuppy: "Thanks. Sir doesn't let me, he insists on Sir, but I prefer Master."

Horny: "Why?" There's another pause.

LuckyPuppy: "I want to be owned."

LuckyPuppy: "Like a pet."

Horny: "I see. So, Puppy, what do you want to do?"

LuckyPuppy: "I do have an idea for that, actually."