There's really not much to say about Bride Wars, and I don't think anyone who reads this is also going to watch Bride Wars, but now that I've seen this particular movie for the second time, I feel as though I need to get some things out of my head.
Comedy writing. I don't claim to be an expert on this topic, but I have noticed some problems with lazy writing that applies not only to this movie, but to many many other things as well. By way of example, Bride Wars uses "Really?" as a punchline of the "what you just said was ridiculous, and I'm not going to dignify it with an actual reply" variety. It's difficult to really call this a punch line, but I think it's where the laugh is supposed to occur, so it qualifies technically. For it to work as a joke, I think it has to act as a segue back to reality following a silly diversion, and the transition needs to make the silliness seem funnier by way of emphasizing how incongruous it is with reality or the actions of normal people. Jerry Seinfeld was on 30 Rock in the last year or two, and he used "really" in this way twice. In one episode! The one use that I remember was when he was riding in an elevator with that one irritating guy who was doing an imitation of the Seinfeld synth and mouth-noise music that accompanied the old show, to which Jerry followed with .... "really?".
In a similar vein is the "who does that" or "what is that", which is a slightly wordier version of "really" that functions in essentially exactly the same way. Someone does or says something wacky, and then that line comes out to drag a laugh out of the reality/silliness contrast. When the Odd-Job knockoff towards the end of Austin Powers throws a deadly shoe at Meyers, there's sort of an homage joke there for the people who know who Odd-Job is, but then there's a bonus joke when Meyers asks "Who throws a shoe?". If there's any humor in that line, I believe it's coming from the sudden return to reality that makes what just happened seem even sillier and also gives us a reason to wonder why anyone ever thought Odd-Job was menacing for throwing a hat. That's kind of funny, right? Laughing at cheesy characters that were at one time taken in earnest? I think it's the same kind of joke as the "quasi-futuristic clothes" or whatever line from earlier in the movie, or when Seth Green questions why they have to set up an elaborate death trap when he could just shoot the spies and get it over with.
He's transporting the contrived (silly) conventions of the spy thriller into reality for comedic effect, which is sort of a broader application of "really". I think Yahtzee had something similar to say about video game humor, which is primarily reliant on taking video game logic and tossing it into reality so we can see the humor in the contrast. I agree with Yahtzee that it's a pretty easy sort of gag to write, and you really don't have to be very clever to come up with it or get it. Saying "really" and "who does that" is, I hope, the laziest form of this joke, and that there is no lazier way to get the same cheap laugh. Maybe having an actor look into the camera and say "just kidding!" would be worse, but I'm not sure.
As an aside, I'm pretty sure that if you're writing for ANY sort of script, and you have a character who begins a line with "it's time [for/to]...", then you are writing a shitty line. Picture Jeremy Irons in Dungeons & Dragons yelling "IT'S TIME TO DIE" and then picture an equals sign, and then recall Darth Vader yelling "NOOOOOOOOOO" in Revenge of the Sith because both line types are exactly as impossible to include in a movie without being completely retarded.
So anyway, that's Bride Wars, tangentially. There's also some crap about treating mundane but carefully orchestrated activities (wedding planning) as though they were dangerous military campaigns as a joke, and a lot of treating weddings and relationships as tightly regulated activities that only girls can understand, participate in, or care about.
Also, I'm surprised that the guy who wrote the dictionary definition of "hysterics" didn't get his name in as a screenwriter for Bride Wars, because he was obviously a strong influence.