KillerKingBakudan

Yeah, they'd know about humans, not about our animals.

That's if Celestia isn't the only one who knows about it.

The thing is they wouldn't know where it came from. If we saw a person behaving like that in real life, we wouldn't assume he's just an animal from another world. We'd think he was mental.

Let's say you had a real pony as a pet. Someone sent you a private invitation to a big award ceremony being held at Canterlot. Naturally, there will be hundreds if not thousands of citizens from every Equestrian city attending. All the princesses, including Twilight and the rest of the Mane Six, are gathering there as well. To get there, you have to go through a portal like the one from Equestria Girls. But again, you retain your human form when you go through. Unexpectedly, your pet pony decides to run after you a few minutes later. It also retains its pony form when it goes through, and no one notices it until it causes quite a ruckus. Everyone in Canterlot will witness this pony as it neighs repeatedly at every equine it sees, running around aimlessly, eating their food, crapping all over the place, and possibly even looking to steal a mate. How would they deal with it?

^ That looks more like a playful noogie to me.

I can say this much. Every topic you can bring up in conversation has a few demographics that should always be kept out of bounds. I won't talk about the show in front of people who don't seem like they'd fit into the fandom. That's like talking about video games in front of old people. I'm honestly not sure I'd fit in myself. I like MLP enough to buy every season on DVD for my niece, and to come here obviously. But I won't go out of my way to attend Brony conventions or buy the merchandise from Hasbro.

Whatever language they speak, Twilight didn't seem to have problems adapting to the way humans spoke in EQ. She only had to work around a subtle difference like "anybody" as opposed to "anypony". But even if they technically did speak a different language than us, Equestria would more than likely provide magic for unicorns to work around those barriers. I think a translation spell that allowed every word spoken from you to be heard in their native language, exactly as you meant it, isn't too big a stretch. Still, it wouldn't necessarily address the cultural differences between your own world and theirs. They know nothing about humans, so they wouldn't understand why you'd want to pet them like you would any other animal. For all we know, it could be like an insult to them.

Okay then, I elaborated a bit more in the OP. We tend to treat most animals like newborn infants. If the ponies ever petted each other, it wouldn't be under the same context. Being that they are intelligent adults with the same verbal communication as ours, they may or may not take kindly to it.

Here's what I mean. You stumble across a portal of some kind and land in Equestria, but unlike in the EQ movies, you retain your human form. None of the inhabitants know who or what you are, but from your behavior, they can tell you're pleased to see them. They don't consider you as a threat, and they're eager to learn more about you and where you're from. Naturally, your first instinct would be to talk to them. And because of your past experiences with animals on Earth, you have an overwhelming urge to pet them. And by that, I mean the works: to stroke, tickle, cuddle and kiss them like they're your precious little babies. But being that ponies are the dominant species in this world, and they care for their own animals the way we do ours, how do you think they would take it? Would they feel uncomfortable? Offended? Or would they think of it as some weird kind of massage therapy? And while we're on the subject, who would you want to pet the most?