Today is Troian Bellisario’s birthday, and we think she deserves some serious recognition for the smarts, sarcasm, and vulnerability she brings to us as Spencer Hastings on Pretty Little Liars. Here’s are five reasons why Spencer is the best Little Liars!

She will find “A”

Or, at least, that seems to be Spencer’s game plan. We can just imagine her chanting it to herself in the mirror when she gets out of bed every morning. In the search for who is hunting her fake-dead bestie and the rest of the Liars, Spence takes no prisoners. Seeing the overachieving genius with a goal is kind of scary (and awesome) whether that goal is acing her French test or taking down a cyber stalker. Lately, it seems to be more of the latter, and we love watching Spencer work through clues and follow trails. She’s like a 21st century Nancy Drew! When it comes down to it, Spencer is really the Liar who drives the PLLers onward in the search for “A,” and that’s why we think she might be the one to make the ultimate reveal happen.

She’s fearless!

Actually, come to think of it, we’re not sure if we’ve ever seen Spencer truly scared. It’s like she goes straight from investigation mode to survival mode without stopping on the “seriously freaking out” mode in between. Examples include: racing up the church clock tower with a murderous Ian on her tail in the Season 1 finale and, more recently, calmly suggesting the Liars will find another way out of the creepy crypt in the Halloween special. She’s such a rational human being that she doesn’t waste her energy on fear or at least, showing it and that’s kind of impressive.

She has the best one-liners.

We’re proud to say that all of our Liars are pretty darn witty, but we think Spence takes the cake when it comes to finding the perfect witticism for any occasion. Whether she’s advising her BFFs on the right course of action (Just be careful and wear sensible shoes.”), suggesting alternate sources of energy (“If only we could harness Mona's sense of entitlement. We could light the eastern seaboard.”), or defending her nerd cred (“I could give you the entire Targaryen speech from the end of [Game of Thrones] season one but I will not waste my breath.”), she knows exactly what to say!

All of Season 3, Episode 19: “What Becomes of the Broken-Hearted”

Or, as we like to call it, the episode in which Spencer both tackled Mona to the ground and started a game of strip trivia. (We love that even Spencer’s mental breakdowns have brainy components.) Basically, Spencer Hastings made the second half of Season 3 unmissable, but “What Becomes of the Broken Hearted” stands out in particular for that way Troian took Spencer believably from stable to unhinged in no seconds flat. It was so convincing that we’re afraid Spencer could have another psychotic break at any moment. And by “worried,” we mean kinda, sorta hoping for - because unstable Spence is super entertaining to watch.

She’s grown into herself.

Credit: ABC Family

It’s been pretty cool to watch Spencer evolve from the pilot’s sarcastic-yet-obedient teenager to a young woman who trusts her instincts and won’t let anyone push her around. The Spencer we first met definitely had a streak of defiance, but would ultimately fall into the Hastings family line. Since then, she has dated Toby against her family’s wishes; forced her father into ‘fessing up about Jason’s paternity; and stood up to “A.” We’ve eager to see where this feisty, independent character goes next!

Do you think Spencer is the best Liar? Why or why not? Sound off in the comments below!

Catch the Pretty Little Liars Season 4 winter premiere, Tuesday, January 7, 2013 at 8 p.m. ET on ABC Family.