Annie Walker is a talented CIA officer. She entered into the CIA because she got "burned by love" when she "let her guard down", a reason that makes Auggie say she "fits the profile" of a typical CIA worker. She is compassionate, and genuinely desires to help those she meets on missions. She speaks seven languages, including Spanish, English, and Russian, and is able to hold her own in a fight.
Doesn't Like Guns: Technically, but it's justified in that 1) she's suppose to be a museum curator in most of her covers so guns would break her cover and 2) she never completed gun training before being brought up from the Farm so she probably isn't even allowed to use a gun unless she's forced to. This is true until post-"Horses to Water" in season 2, she specifically asks Joan to get "shooter and bodyguard" training. Blown totally to bits as of season 4's "Dig for Fire, when it's revealed that she's now routinely carrying on US soil, technically against the CIA's rules, because she nearly died from a gunshot wound received in season 3's "Glass Spider".
Sexual Extortion: She sees no problem in seducing male contacts to build a rapport, such as the apparent Big Bad of Season 3. As Lena points out however, the CIA has a bit of a self-aware Double Standard when it comes to this, so it doesn't mind.
You, Get Me Coffee: She gets upgraded to walk-in work, though! And then lunch duty! And it is always noted that whenever she goes into the field, it's limited to situations where her skills would be useful such as being a liaison.
Played by Christopher Gorham
Auggie Anderson worked as a CIA special operative, but was blinded on a mission in Iraq. As he put it, he got out to look at what he thought was a dead dog, and the "next thing [he] knew, [he] was Ray Charles". This turns out not to be true.
Byronic Hero: He's the Nice Guy version of this. Intelligent and charismatic? Check, Dark events in his past that he feels the need to atone for? Check. Resistance to authority? Check. Cynical and Jaded? It's subtle but it's there.
My Guy Back Home: To Annie on a lot of episodes as he typically has to stay home while she goes on missions. Occasionally they work together in the field and once in a while it is Annie who is the Girl Back Home.
Nerds Are Virgins: Awesomely subverted with Auggie, who is most certainly a ladies' man.
Dangerously Genre Savvy: As soon as she's polygraphed, she pieces together why Arthur set things up the way he did. Though she admits she had no idea him having a son from an old relationship 30-some years before was even likely.
First thing Joan does when she meets Annie after months of thinking her former operative dead? Gives her a hug, administers first aid, and asks if she needs cash.
Pregnant Badass: In Into the Fire she cleans up a crime scene, cracks a safe, blackmails a senator in the middle of a Senate Intelligence Committee meeting, and then gets promoted, thus becoming the CIA's highest ranked female employee ever.
Reasonable Authority Figure: At least to her own people. Not so much when other agencies get involved, most notably the FBI, at least from their perspective.
Played by Sendhil Ramamurthy
His father was the head of the CIA. Because of this, he seems to have issues relating to people in the workplace. He was also sent to befriend Annie to get information about Ben Mercer from her.
Ambiguously Brown: Lampshaded. Jai is played by Chicago native of Indian descent Sendhil Ramamurthy: his father is white and his mother's ethnicity has not been elaborated upon, and Annie's sister calls him "the George Clooney of... wherever he's from!"
Anti-Hero: He's much more morally gray than either Auggie or Annie.
But Not Too Foreign: His father is from America and he met his mother in India while the former was stationed in the country as a CIA agent.
Your Cheating Heart: Joan was his mistress before he divorced his wife. Thus, one of the few things Joan is concerned about is that Arthur's going to stray again.
Played by Hill Harper
Calder is initially the station chief in Colombia, but rapidly moves up the promotion ranks in the CIA. As a consequence he becomes a thorn in Annie's and Auggie's sides.
Jerk Ass: He's been an ass to everyone he's come into contact with. However, he's shown to have his noble sides.
Wild Card: He appears initially to be working for Henry Wilcox. However, the truth is, he's not wholly on anybody's side. He's after "the truth", as he sees it. It just so happens that dovetails with Annie's mission of getting rid of Henry.
Played by Anne Dudek
Danielle Brooks is Annie Walker's sister. She is married, has two children (both girls), and lets Annie live in her guest house.
Ben Mercer is a wanted person by the CIA. He and Annie Walker spent three weeks together in Sri Lanka, and fell deeply in love, but he left in the middle of the night, only leaving a note which read, "The truth is complicated, forgive me".
Decapitated Army: At one point head of a sprawling corporate espionage empire with moles seemingly everywhere, he has since been reduced to seeking asylum in China, but before he can get out of Hong Kong, Annie shoots and kills him.
Even Evil Has Loved Ones/Even Evil Has Standards: Is genuinely shocked and saddened by the idea that he would sacrifice his own son for his Chessmaster schemes. He seems to care for his ex-wife, but it has a possessive edge to it as revealed in Season 4.
Played by Oded Fehr
Eyal Levin is a Mossad agent who has frequently crossed paths with Annie and have worked together on several joint CIA-Mossad operations.
With Friends Like These...: Whenever we see him he has a hidden agenda that is somehow opposed to the United States' best interest. He's more or less a good guy but that doesn't stop him from lying to and manipulating the Americans to make sure Israel comes out ahead.
Played by Sarah Clarke
Lena Smith is the head of a rival departmant to Joan's. She recruits Annie into her department to seduce and turn Russian FSB agent Simon Fischer, but is eventually revealed to be a FSB double agent when she executes Simon and tries to frame Annie as a mole. She is later hunted down and killed by Annie in Moscow.