There's a little trilling/chirping noise that I often use when I'm greeting Gizmo. It's nothing too fancy, but it is distinctive, and so far as he's concerned I'm the only human in the whole world who "calls" him that way. It's how I usually tell him good morning, how I say hello when I get home, how I answer him when he's doing his "Come play with me!" warble. It's an all-purpose greeting with very positive connotations, and can mean anything from "Hello!" to "Let's play!" to "I see you!".
Well, recently, I've been fighting a sinus infection, and it's had a pretty drastic effect on my voice. Without thinking, I tried to trill at Gizmo anyway, but the sound didn't come out right. It was more of a broken squawk than anything else. Clearly not the sound I've been greeting him with his whole life.
The response was instantaneous, and really quite interesting. He laid his ears back, and shrank away from me, giving me an incredibly wary, suspicious look. When I entered his play pen to play with him, he let out a wail and ran and hid in his play tube. I looked in after him, only to see him crouched at the back, whining and giving me the stink eye. No amount of coaxing could get him to come out.
He doesn't mind playing with me if I forget to trill, but apparently I'm not allowed to trill and get it wrong. After all, if I can't do the "mommy" trill correctly, I must really be an impostor.