All of the stupid shit Dana Walsh did by helping Kevin Wade with the robbery instead of just telling Hastings she lied about her past and identity makes perfect sense because she's The Mole and is trying to maintain her cover.
What. Revealing Starbuck as a mole makes all of her prior actions inconsistent. Not just straight up murdering Kevin the moment he threatened her cover like she did with the parole officer, assisting in the robbery by shutting down the cameras and giving them an access card using her administrative privileges, an action that would certainly lead to an investigation of her, and not going to Hastings or Cole and saying, "Hey, this guy I used to know is harassing me. Could you take care of that, and make sure not to believe anything he says about me because he'll do anything to stay out of prision? Thanks," so she could consistently stay at CTU and actually assist the terrorists as a mole rather than dicking around with her personal bullshit are all out of step with the Ass Pull of her being a mole. You could make the point that, up until then, she hadn't actually done anything to assist terrorist endeavors such as redirecting CTU Field Ops away from President Hassan so the car bombing actually worked or using her influence over Cole as his lover to keep him out of the field, so she had time for all that, but that strikes me as specious.
Ultimately, Dana was attempting to stall her inevitable outing just long enough to fulfill her end of the bargain. Telling Hastings about her past would result (in the best case) with her getting fired and thus unable to help Samir. Every time she met with Kevin (except for the last one, of course) she was not in a position to easily get away with killing him, and would jeopardize herself if she caused Kevin to get captured. Don't get me wrong, I join the 24 fans who loathe this poorly-executed subplot, but in retrospect she was given a bad option and a worse option, and she chose the one that would buy her the most time. She wasn't looking to stay out of suspicion forever, just long enough.
She could have easily just called up her terrorist buddies, said "Yeah, I got a problem I need you to take care of so the mission won't fail" and that would be that.
It did however seem like she still had feelings for Kevin in the last episodes of that storyline so maybe she wanted to get rid of him without killing him?
Not that it makes the revelation that Graem is Jack's brother any less idiotic, but having him address a sitting president by his first name was an oddly effective way of conveying the fact that the lone name we were given in Season 5 is a first name, not a surname. The Reveal that his surname was Bauer would've been one of the best twists of the entire show if not for the fact that he and President Logan both referred to Jack solely by his surname in all of their conversations, which suggests that Logan didn't even know Graem's last name and that Graem was deliberately trying to conceal that fact, which seems highly unlikely given that Logan's position isn't exactly one where you can afford to conspire with someone whose full name you don't even know.
The way President Hassan was killed off was perfect when you consider that the writers had previously been ordered to never kill off a sitting president on screen (see:the ambiguous fates of Keeler and Wayne Palmer, although the latter was confirmed dead in Redemption by way of a newspaper article). We the viewers get to see the internet feed that the terrorists set up, but then Jack and Renee bust in and seemingly stop the villains in time, only to realize that the video is still running and that it was pre-taped; President Hassan is already dead. While we are shown the dead body, we do not see the end of the pre-taped execution video, and so the mandate that no sitting president be killed off onscreen—even a president of a fictitious nation, rather than the United States presidents that were previously grievously wounded while in office—is still technically met.
The Season 7 revelation that Michelle was pregnant when she was killed, just like Teri was, carries quite a bit more weight when you realize how much Jack and Tony have run into similar situations with their wives. Both separate from their wives in the wake of personal difficulties (Operation Nightfall for Jack, prison for Tony), both are forced to work for terrorists when their wives are taken hostage (Jack is forced to help Palmer's assassins, and Tony is forced to enable Saunders to escape) and both seek revenge against their wives' killers, with the main difference between the two being that Tony always puts his wife first, while Jack tries to Take a Third Option.
One major criticism of Curtis' death in Season 6 is that it was pointless, since the whole reason for it was to save Hamri Al-Assad, who died several hours later anyway. However, this allowed Assad to stick around long enough to tell CTU about Dmitri Gredenko, which in turn affected later plots in the season. So, though it is long-winded and though his motivation for wanting to kill Assad was still contrived, Curtis' death served a purpose after all.
It's probably unintentional, but Jack's name takes on an additional meaning if you know some terminology from card games. In Euchre, cards are ranked from nine, the least valuable, to ace, the most valuable, with cards of the "trump" suit more automatically more valuable than any other card of another suit. However, another rule is that the jack of the trump suit and the jack of the suit which is the same colour as the trump suit become the most valuable cards in the game, even more than the queen, king and ace of trump. The trump jack, the more powerful of the two, is known as the "right bower", and the other black/red jack, the weaker of the two, is known as the "left bower". In short, the jacks, also known as the "bowers", are the most powerful cards in the game. So Jack Bauer is literally a trump card.
The realization that Jack likely would have tortured Renee Walker's murdererregardless of whether he had any information about his employers. Considering just how enraged Jack was for this whole portion of the series, as it goes on it's clear that if he hadn't had any leads to follow up on, Jack would have just put the guy through hell just to see him in agony, and in spite of his claims that he'll make it quick it he told him everything (he didn't, hence why Jack drug the torture out) the fact that he'd already lied several times regarding his goals about dealing with the conspiracy is a strong indicator that his promise to let Pavel die quickly were also false. And that leads to the next horrific realization: In the end, Jack discovered that he swallowed a data card that in turn led him to Logan, and cut the guy's stomach open and let him bleed to death from the wound both to get the card and so he could suffer a similar fate as Renee. If he hadn't had that data card, and considering that he wanted this guy to die in agony like Renee had.... what would he have done to kill him instead?
According to Word of God, even though she did not appear nor was she mentioned after the events of Season 6, Karen Hayes remained married to Bill. With that in mind, since Bill died halfway through Season 7 helping to save the President you know that sooner or later she's going to get some unfortunate news delivered to her around that time.
In the Season 1 finale, Jack goes to confront the Drazens, unaware that their leverage, Kim, has escaped. Worried that Jack won't come without proof, the Drazens have Nina tell Jack that Kim's body was found, which backfires when Jack goes in guns blazing and kills the Drazens. However, right before Nina gives Jack the news, he quickly says he is going in to rescue Kim. This means that Nina had no reason to tell him about Kim's death; if she had kept her mouth shut, Jack would likely be dead and nobody would know of Nina's treason.
In the finale of Day 9, Heller learning of Audrey's death is bad enough, but it's even worse if you remember that Audrey was previously presumed dead between Days 5 and 6, meaning this is the second time Heller has to mourn his daughter.
Towards the end of Season 6, when CTU is being taken over by Zhou's mercenaries, Milo Pressman lies to him and says he's in command of CTU. A few seconds later, Zhou points a gun at Milo and shoots him in the face. Several minutes later, Zhou finds out Milo was lying and that Nadia's the one in command. He doesn't even touch her. Umm, okay.
Zhou killed who he believed to be in command as a demonstration to the other hostages. He had already made his point when he discovered the deception, which by now was in a private setting. Killing Nadia would have served no purpose. You can look on it as a brutal but pragmatic mercenary not wanting to waste a bullet on an unarmed woman, or as a complete monster who thought letting her live with the guilt would have been crueler.
In Season 3, Nina confirms the authenticity of the virus with a machine. That machine had to operate on specs supplied by the sellers, rendering any promises it could make completely worthless.
In 3x13, Nina's computer worm threatens to compromise CTU files and they don't know how to stop it. Apparently, they forgot the power switch.
Again in 3x13, Sherry wants to send Alan to jail, and so she needs his phone records. Rather than calling the police (or the President, who she's working for) she goes to his house and asks his wife Julia to steal his cellphone. A very refrigerated episode.