What you also see is a group of women from another large booth promoting another media property. I believe (if I remember correctly) they were connected to The Green Lantern somehow, though I might be mistaken. To drum up business for their booth, they stormed the stage as soon as the Just Dance 3 people asked for volunteers and played it up for the crowd.
When you're dealing with such a large convention, you need to have a draw. For some, it's the so-called "booth babes." These are (typically) hired models or actors brought in because they look good and can play to a crowd. They wear form fitting costumes and try to convince you that you need what they're selling. These booths always draw a crowd of eager fans with cameras.
But a hook at a convention like this doesn't need to be that extravagant. Another popular tactic is a raffle or giveaway game. All you need to do is sign up for the mailing list and you receive the chance to win free stuff. I don't know what I'd do with a size medium t-shirt signed by the cast of Attack of the Show, but that didn't stop me from putting down my name and e-mail for a shot at the prize. Other booths use spinning game wheels and have a huge stack of small prizes to give away. Still other booths offer up extras on a purchase (or free swag) if you sign your name. It's a way to pad their mailing list in exchange for an inexpensive tangible good.
Still others have one employee stand outside the booth and try to drag people in. The best ones make eye contact with you and figure out a friendly introduction to the product. The man answering questions about the MakerBot Thing-o-Matic--a home 3D printer--was especially effective. He did not bother you unless you stopped to look at the printer. Then he answered any question you had with simple technical language. He had clearly rehearsed his soundbites enough to deliver them naturally. I'll be trying to harass him again later today for a more in-depth interview if I can find the time.
The last strategy is the riskiest: letting the work speak for itself. These are the booths--usually in Artist's Alley--that let you walk up to them. I wound up getting into a very nice conversation with a couple from Canada that were selling beautiful tabloid-sized poster prints of his original artwork. They came down to the convention more or less on a whim and thought they'd give it a try. By the time I got there, they had already run out of change and were offering deals as a stall tactic while one or the other ran off to bum change off of other vendors. The work they brought was so beautifully displayed and catching that it became as big a draw as the booth babes. There were always two or three people standing around their booth flipping through their portfolios.
Promotion is a tricky thing. If you come across as cold, unfriendly, or calculating, you aren't going to do well (unless you are a big name draw). However, everyone needs to calculate their own strategy or risk being completely overwhelmed. It's a delicate balancing act that can change from minute to minute at a show like NYCC.