Wouldn't you notice if you were inhaling liquid nitrogen?
Yes, but one good breath would still probably kill you. It wouldn't look like it did in the show - the cause of death would be massive internal damage, not Human Popsicleitis, and it wouldn't be instant, but the plan would work.
What happened to Charlie's ex? Was I not paying attention, or did she just disappear from the show for no reason? Also, why was she even in it? She never did anything. Come to think of it, why was Rachel in the show? She was effective as a plot point but she never did anything after Charlie found her. I know they're probably just part of some aborted arcs, but it still bothers me.
The way I get it is that they put in his ex to show that there were still some things he couldn't have, even with fifty million dollars and his job back. No matter what he did for her, he didn't get her back, and it was crucial in pointing out that his life wasn't going to go back to the way it was just because he was proved to be innocent. Rachel's entire purpose was to be a Damsel in Distress- she never did anything, but she didn't have to, because her existence- once Charlie found her- threatened Jack Reese and the other guys who set Charlie up. Remember what Jack Reese said in Season 2: 'I have the girl. While I have the girl, we control Crews'. Once Charlie had Rachel, they couldn't control him, so they were effectively doomed.
That being said, Rachel's exit in particular probably could have been delayed, if only because they clearly sped up the development of her relationship with Crews in a way that makes you feel they skipped a big Rachel episode (or cut a lot out of "Evil... and His Brother Ziggy."
What was with Reese's random sexing up during season two? She went from dressing realistically for a detective's 12 hour work day (comfortable pants and shoes, button up shirts, little make-up and hair back in a bun) to running around crime scenes in heels and wearing tops low enough that her partner (in one of the most randomly annoying moments on the show) advises her to button up because she's a lamb chop or something.
An attempt to add more viewer interest?
Who was the anonymous video interviewer? Season two establishes that he really exists since they find his body after Roman kills him, but this raises all sorts of creepy questions of who he could possibly be to know so many details of the show's plots.
Probably just a random guy making a documentary. He was probably a very respected journalist, given that so many people were willing to talk to him, but otherwise, I got nothing.
Ted and Crews met in prison—in Pelican Bay, which is a supermax prison. Crews was a convicted murderer, so it makes sense, but why was Ted, a white collar criminal, in superman?
He was the CEO of a big company who got arrested for insider trading. My guess is that the writers felt that his crime would be serious enough to land him in supermax.
Pelican Bay has both a Supermax and a general population facility. Crews met Ted, in genpop, before the abuse by the other prisoners got so bad that Crews was moved to the secure housing unit for his own safety. As for why a white collar criminal would be in a maximum security prison at all, many Federal prisons have a small minimum security satellite camp that fills maintenance duties for the facility.
Why didn't someone just kill Roman? If everyone working for him was doing it out of fear for themselves or their family, why didn't they just kill him? Then the threat would be gone. That's exactly how Crews solved the problem in the series finale.