I think it's been a while since we've had a character discussion here, but let's finish up this thread with a good one, shall we?
Caution: dangerous amount of over-analysis ahead!
Also, unmarked spoilers for Season 2 Episode 18 here.
PINKIE PIE!
Yes, in all caps and bold. I read something interesting about The Pink One over at Giant in the Playground. That Cranky is right. She IS much smarter than she looks. In fact, she's hyper-intelligent. With emphasis on "hyper". Yeah, I know. Pinkie Pie? Intelligent? But bear with me for a second here.
Pinkie Pie said in the first episode that she knows everypony in Ponyville. Which sounds like hyperbole, but as this episode revealed, it is not. She DOES in fact, know everypony in Ponyville. And she doesn't just know everypony, she knows several details about each. Rattling off birthdays is something she does casually, and the resolution of this episode came solely because Pinkie remembered some small detail about Matilda that nopony else really could have known. Just how good a memory does she have? Also, just how aware of her surroundings is she? Well, let's call back to the first episode again. Pinkie meets Twilight. In the few seconds from "Hello?" to Pinkie gasping and rushing off she realized the following: "New pony! Doesn't know anyone in Ponyville! Must help! Throw a party!" and she even found out that Twilight lived at the library. That's Batman or Sherlock Holmes level awareness. One look at the new pony, and she had her pegged. However, Pinkie is not Sherlock Holmes. She doesn't appear aware that she can do this, it just happens. And her responses to it are not always thought through. I mean, she could at least have said "Hi!" back.
And this is a recurring thing, too. Pinkie has an amazing talent of having all the facts and coming to a wrong conclusion. No, it's not time to mock Nightmare Moon. No, Gilda doesn't want to be your friend. Yes, getting a dragon to laugh is a good plan, but dressed like that? Yes, your friends are hiding something from you, no it's not a sinister plot against you. Yes, keeping a Pinkie Promise is serious, but Rarity and Fluttershy really needed to know this. No, a song doesn't count as a peace negotiation. It's not THAT kind of party. Maybe Princess Luna could be a little sensitive about the whole Nightmare Moon thing? There's a time to be a playmate for the babies and there's a time to be a caretaker. It's not the same. Anyway, you get the idea. But then there are the moments when she shows that she really does pay attention. Who finds the Elements of Harmony guide? "It was under EEEE!" Who immediately knows how to deal with Parasprites? Who knew that there was a flight spell in one of Twilight's books, despite only having have it fall on her face for a few seconds? And in the latest episode, who knew that two people in the town were looking for each other? That would be Pinkie Pie.
So, Pinkie Pie seems to me, to have an awareness of her surroundings bordering on the extreme, but... she doesn't realize it's anything special. She just thinks and senses at a much faster rate than most ponies, and she always has, so it's not something she's conscious about. It sounds a bit odd, I'll admit, but this would explain a lot.
First of all, Pinkie doesn't know it's a cartoon, yet all the cartoon antics she does? She just knows it's possible. Don't ask her how, she couldn't tell you, but she perceives reality differently than most ponies. Which does lead to the amusing idea that every pony could do it, if they didn't know they couldn't. It sounds crazy, and it is, but it kind of works, too.
And secondly, this explains the Pinkie Sense. Yup, the Pinkie Sense makes sense. Pinkie, if she is hyper aware, yet doesn't know it, will subconsciously detect certain patterns. Falling objects, ponies about to open doors, and even when a pony is about to have a change of heart. She doesn't know, but she feels it will happen. Twitchy tail and all the other tells? Simply a response to outside stimuli that Pinkie doesn't know she can sense.
And yes, I am aware that I just wrote that much about the mental state of a pink cartoon pony. I just found the idea interesting.