Lady Gaga in the meat costume
Let's face it - Lady Gaga will be overdone in general, but the infamous meat costume she wore to MTV's Video Music Awards has to be the worst idea possible. Fresh meat may seem fine at the beginning of the evening when it is still cold, but by the end of the night you will stink and likely be surrounded by flies. No one really wants to hang out with Pig Pen from Peanuts. Plus, how do you attach that much raw steak to your body? Lady Gaga has a team of wardrobe consultants to do so; you probably do not. This seems like an outfit begging for a severe wardrobe malfunction (on many levels), which no amount of alcohol could make better.
Anyone from the Jersey Shore
Again, these characters will likely be overdone this year, and really, haven't we had enough of Snooki, The Situation et al? Plus, you will feel sad if you have to fake abs to look like The Situation and if you don't, well, you will just look like a show-off. There also might be a self-tanner and hairspray shortage in the city of Louisville if too many people decide to dress up as Snooki. Let's let people with other costume ideas share the products - people going as pumpkins might need some of that orange glow!
Anyone from the Mad Men cast (especially the men)
Yes, it's easy. Put on a suit. Here's the problem - it's too easy. You will just look like you over-dressed for your party. Unless you have a striking resemblance to Jon Hamm, skip it and find something that requires a bit more creativity. Also, the show has been on for a while. Try dressing up as someone from a show that has been on for less than three years.
The Twilight Cast
This is a combination of all of the above. It is a) overdone, b) fairly easy (jeans, t-shirt, vampire teeth), and c) a bit dated. The first Twilight movie came out in 2008. Though your teenage cousin may still be caught up in the team Jacob vs. Edward debate, it is time for you to move on.
