On the other hand…my mom and my sister look exactly alike. My sister came to visit. Chuckie was all over my sister. She was my mom’s cat, and loved sitting on her lap. My mom was in the dining room. Chuckie heard her voice…took a double take at my sister, and freaked out!
Smell could also be a factor…I know Trilly reconizes my sister and does her figure eight dance, to her even thoug Trilly is scared of strangers and my sister doesn’t live at home.
Smell is much more important. Not only is a dog’s sense of smell much more sensitive than a human’s, it’s also much more selective. High selectivity means that dogs can dissect everything they smell into it’s component parts for the purpose of winnowing out certain smells. For this reason, the use of “masking scents” by drug dealers often fail. Highly trained drug finding dogs can search out certain scents while ignoring everything else. They pretty much have to; if they had highly sensitive noses but not highly selective ones, they’d get overwhelmed by all the smells. High selectivity helps them get around that problem.
I was sitting at home one day and decided to shave my head. I was wearing a hooded sweatshirt at the time. I went upstairs, shaved my head, showered, put hooded sweatshirt back on, put hood over head, came back downstairs. My pit/lab mix dog was sitting in the living room. I walked right past him.
I went outside for a moment and came back in. When I entered the living room I took the hood off. My dog got up to see what I was opening the door for. He saw a strange bald guy walking into the living room, his scruff went up and he jumped at him (me). He wasn’t planning on killing me, but he was definitely firing a warning shot over my (the strangers) bow.
When I said his name and laughed, he went into an ass-ileptic fit and started licking my hands.
He is protective of the house and I suspect if I had been gone and came back with a shaved head, somehow managed to have entered without him knowing, and he walked into the living room and saw me there, I think I might have been bit if I surprised him. (for the record, he has never bit anyone, or me, before)
My other dog didn’t notice I had shaved my head. It could be because she’s seen me like that in the past. In fact, I think my head was shaved when we got her.
I can put on a hat and my dog used to freak out.
Now it takes a hat and sunglasses. 
On the other other hand, I look nothing like my mother yet I sound exactly like her. Her cats looooove me, but they always do the cat version of a double take (look and stop purring) once they look at me. Once they realize I’m a scratch whore, they go back to hoping for a happy ending.
Obviously he was trying to save her from embarrassment by telling her to not leave the house like that. 
My dad had a grim reaper costume he got for Halloween one year. When he put it on, or even just the mask part, the dogs would FLIP. growling, barking, the whole bit. Soon as he took it off, though, they’d be fine. So, I do think faces are important, at least to dogs.
My beautiful and very dim cat Juliet freaks out and runs like holy hell if she happens to see me carrying something that changes my outline, let alone wear something that changes my shape. :rolleyes:
I’ve wondered a few times if she needs kitty Prozac, but her eyesight seems to work just fine based on testing with kitty toys.
I can put on a mud masque and my dog will do a double take, so - yah, not so much, at least for my little guy.