Yes, this is what I’d think as well.
The OP THOUGHT she couldn’t hear him because, ya know, the window was closed. Thats mostly very likely why he said what he said after the window closed. Therefore, most very likely he did not intend for anybody other than the dog to hear it. And the fact he was embarassed afterwards indicates this wasn’t some sneaky backhanded way of hitting on her.
She was probably skeeved because she thought the OP was a furry looking for a threesome 
Not gonna happen. I doubt I’ve eaten Wendy’s food 5 times in my life. As I said, I rarely eat fast food.
Yeah, and it is pretty clear that the OP though he was by himself.
Wait… I’m a furry because I talk to my dog?
That’s a bit of a leap, isn’t it?
OK, seriously, I am going to say this one last time.
It’s not about what the OP thought or intended, it is about what was perceived by others.
Objectively speaking and knowing nothing about what was intended by the OP (because the counter girl knew nothing of what was intended by the OP), and considering that his tone was in fact audible and he appeared to be talking loudly to his dog on the subject of her looks, his behavior appeared at the least, strange.
Note that I say his behavior appeared strange, not that it was actually strange in the context of facts only he knew inside his own head. To the person observing that apparent strangeness, it’s offputting. Cause I’ll you what, when I’ve worked retail the one thing I’ve never had any desire to do was to find out more about the motivations of people acting strangely. I wanted them to get gone.
I would not have been skeeved out at overhearing someone thought I was cute. I was pretty darn cute back in the day and I used to get hit on by “old guys” and even that didn’t really skeeve me out, more just made me laugh at their patheticness.
But you didn’t hit on her, you made a passing remark to your dog about how cute she was. I doubt she was flattered or skeeved. She probably just laughed and told her friend, how that old guy thought she was cute.
That was a joke sonny (the smiley at the end is a hint).
Rut roh, Raggy. Zoinks! I think we skeeved her out!
Ah. OK.
And yes, I do talk to my dog. He’s the only one who understands me.
And he speaks Korean better than English. I should have made my comments to him in that language, but I didn’t.
Its offputting to people that think and reason like you do. Not all people do that.
It’s true not all people reason like me. But the OP asked for opinions, and mine is shared by kmshrader, Bad News Baboon, Cat Whisperer, Martin Hyde, Zulema, Sierra Indigo, chela… all agree that it was offputting or something that causes one’s guard to go up when you are a retail worker.
Truthfully, that was what I was not hoping to hear. I didn’t mean to ruin the poor girl’s day at all.
I blame the dog!
I’m SURE you didn’t ruin anyone’s day. Like I said “strange” and “offputting” not “threatening” and “frightening.” It was just one of those things that make you go “whuuu…?” and then tell your friend, “that old guy who ordered the Spicey chicken sandwhich told his dog I was hot. Really loud. Okayyy.” And she says, “what happened then?” and you say, “Nothing, he drove off.” And then you both shake your heads about it and move on.
Believe me, people have acted way weirder, way scarier, and way more inappropriate at your average Wendy’s. Don’t beat yourself up over it.
Wouldn’t have bothered me in the least.
If the girl really is as pretty as the OP says she is (and I have no reason to doubt him) I’m sure she gets graphic/rude comments fairly regularly. An older fellow telling his dog he thought the server was cute probably didn’t even ping her radar.
Back when I was young and foxy that type of comment didn’t bother me in the least (gross or lewd ones did).
If its offputting to some, well its offputting to some, that is true. But you’re trying to make it more offputting specifically because the guy talked to the dog. That IMO is just silly. Most dog owners do that now and then. And even people that don’t have a dog or talk to their dog have probably often seen people that do. And note, you didn’t just say something like “talking to a dog is a little odd”, you used the word “insane”.
I think whats happening here is you found the comment (or even the thought of the comment, had it not even been heard) skeevy and are trying to use the dog as an addtional justification of just how skeevy it is.
And for that matter I’d say people who think people who talk to dogs very strange are hipocrites because I’d bet good money most of em have had words come out of their mouths even when nobody else was around to hear it.
I didn’t say it really loud. If anything, it was a little softer than normal conversation…
Have you asked your dog?
I think that most nineteen year old girls see OLD GEEZER and nothing else, when some man who is more than ten years older them hoves into view. Unless the man in question made it his business to chat me up or touch me when I was 19, he was completely invisible. Apart from as a person who wanted me to sell the something in the shop I worked at.
If the police had ever needed to question me about some sort of criminal activity and the perpetrator was a 35 year old man and I’d sold him cigarettes/gum/a paper earlier that day, no way and no how would I have been able to describe him. All old fellers looked the same to me, just, well, old. Old an insignificant. It would be different if they were a film star or something but I never met any of those. At least, I don’t think I did. I might not have noticed. 
So I doubt you ruined her day and I doubt she was flattered, you were most likely just part of the scenery. A customer who wants serving. Maybe she might have seen you talking to your dog. If she liked dogs, she might have thought this nice. If she didn’t like dogs, she might have thought this weird. But it would be the act of talking the dog that might have made you impinge on her consciousness, not what you said, if she even heard it. That’s me looking at the 19 year old me, from a distance of getting on for thirty years.
I’d forget about it, if I was you. Nothing to worry about. But if you convince yourself that you migt have offended her and go back to apologise about it, that there is when you will most certainly have some sort of an effect on her.
I think you greatly misunderstood me then.
Imagine a guy sitting across from you on the bus pulls a pet hamster out of his jacket pocket and says to it, loud enough for you to hear, “see that guy over there? He is soooooo hot.”
Do you think he’s
a) Trying to tell you something/make sure you know his opinion
b) Maybe a little mentally off
c) Just having a totally normal, public conversation with his pet, specifically about you and your good looks.
There is nothing inherently insane about talking to your dog alone, without expecting an answer, or about talking to your dog in public about dog-themed topics. Just like there is nothing strange about practicing ventriloquism in the sanctity of your living room. But when you talk AT your pet about other people’s bodies, or, for example, to your ventriloquist dummy in the Wendy’s such that those other people can hear you talking about them, you are acting strange. Again, you give the appearance that you are either
a)intending for the listener to hear what you have to say about their looks
or
b) delusional
I have said all these things repeatedly, so, if you can’t figure them out, I’m done trying to explain myself.