Hey hey! Question because I just saw the new part of the comic you posted;)
Does Pietro prefer being human around Bobby, or does he prefer his big merman form? I'd understand either way, to be honest.
I think... He doesn't necessarily prefer being human so much as he prefers being smaller. He likes how they can touch and be intimate when they're the same size. He's not overbearing and dangerous just being around him. He feels... at home.
Although I did think recently if Pietro asked on paper to Bobby "Do you love me more as a human?" and Bobby would feel a bit sad, but his answer is obvious: He loved him before he was human. Being human just makes things a bit more convenient, but his feelings hadn't changed because of it. My dude had made it work even when he was 80ft long and could only live in the water. He was gonna get a house by the sea just so he could always be close to him. Bobby was always dedicated.
