Like a non-sequitur, a pre-sequitur doesn't follow what immediately preceded it, but instead relates to something that came much earlier. It is a sudden or jarring break in the chronology, but it does follow... when you remember what it refers to.
Jen: Why did you leave Los Angeles?
Keith: Well... have you ever lived there?
Jen: I visited once, for a week. I liked the street performers on the boardwalk...
Keith: Oh, the boardwalk is where I got this red scarf!
Jen: I was trying to knit a scarf just like that last year but I never finished.
Keith: Where do you get yarn around here?
Jen: There's a good store just a few blocks from here, wanna come see?
... ten minutes later ...
Jen: Huh, do you smell Indian food?
Keith: Hmm, not really... but now I'm in the mood to get some Indian Food.
Jen: Sure, let's!
Keith: It was the pollution, that's why.
Keith: Yeah, I wanted somewhere with real air, and LA wasn't it!
Jen: Oh, why you left Los Angeles
Awe-inspiringly clueless gall or chutzpah. An action or utterance that appears to come from an outrageous ego coupled with a breathtaking sense of entitlement combined with complete lack of awareness.
People can show chutzpah consciously. People can "have the nerve" to do something while knowing they're taking a chance. But to show *real* blagojevich, someone almost has to have the blindly arrogant self-confidence that comes from really believing they're right, and having no clue that they might be mistaken.
The canonical example is former Illinois Governor Rod Blagojevich, who was arrested and impeached after recordings of him were made public, in which he discussed his desire to get money, jobs, or other favors in exchange for appointing someone to a vacant Senate seat, and angrily swore at those who expected him to "give away" the appointment for nothing.
Despite this, he had the blagojevich to compare himself to Ghandi, his arrest to Pearl Harbor, and to say that it was "an honor to fall on principle on behalf of the people."
Not only did he never tell me that he'd tested positive before we had sex... but now he's suing me for harassment telling other people about it!
Wow, the blagojevich of that man!
The sort of unfortunate or amusing coincidence or contradiction that you're tempted to label "irony", but realize isn't actually ironic at all. Named for Alanis Morisette, whose song Ironic contains many examples of alany and none of irony (except for the song as a whole, which is ironic...).
You plan a trip to a faraway city, contact your friend who lives there who you haven't seen in months, and find out she's actually going to be visiting your city that same weekend, so you'll miss each other. Such alany!
It's spring, the weather turns warn, and for the first time in many months all the cute people wandering around the street/mall/food court/city park/farmers market/etc. are wearing light clothing revealing faces, arms, legs, cleavage... The more of them distract you, the more often you turn to look, the more likely you are to get bisexual whiplash.
Straight people can get it too, of course, but being bi doubles your vulnerability.
The cute people are out today! I went to get some food and got bisexual whiplash just trying to cross the street.
To Libby (verb): to out someone's undercover role, as Lewis "Scooter" Libby (and others) did to CIA agent Valerie Plame
Her: Yes, I'm sort of a secret agent.
Him: Well, if you keep telling people it's not much of a secret is it?
Her: Oh, you're right! I need to work on my stealth. Sorry.
Him: Don't apologize to me - I'm not the one who Libbyed you.
"Somebody Else's Problem", an effectively-magical field that obscures things you think aren't relevant to you, such that even though you see them (or hear them or read them) you don't actually *notice*, and quickly forget.
More generally, the phenomenon that causes people to ignore issues that they know about but think of as either not something they can do anything about, or not personally relevant to them right now. This can result in something that's very important to a group of people being ignored by every individual member of that group.
Popularized by Douglas Adams in the "Hitchhikers Guide to the Galaxy" series, in which Ford Prefect describes it as:
"An SEP is something we can't see, or don't see, or our brain doesn't let us see, because we think that it's somebody else's problem.... The brain just edits it out, it's like a blind spot. If you look at it directly you won't see it unless you know precisely what it is. Your only hope is to catch it by surprise out of the corner of your eye."
In that series, a strange object can be effectively hidden from view while out in plain sight, by an "SEP field", which "relies on people's natural predisposition not to see anything they don't want to, weren't expecting, or can't explain."
It's just been sitting there all day, hundreds of people have walked by, and nobody said anything or even turned to look! It's like it's got an SEP field around it.
When two people are cuddling in bed, three arms have somewhere to be but the fourth arm is in the way. It's the extra arm.
"I've always wondered exactly what to do with that extra arm. I've tried curling it up between us, putting it above my head under the pillow, straightening it between us and the only thing that seems to work is just putting it behind me."
-- metafilter posting