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When you enter Tophatter‘s site or mobile app, it looks like a scene from a 90s simulator game. A room of (mostly) female avatars face forward, their cartoon-y heads attentively watching an auction on stage. One avatar at the front hops up and down next to the robotic auctioneer, shouting descriptions about their item to the crowd until the highest bidder is chosen.

The whole thing happens in the span of 90 seconds on average, and it’s a weird cross between turntable.fm and eBay. This is the product that once buzzy Blippy — the Twitter for your credit card purchases — pivoted into two years ago.

Surprisingly, the 90s-esque avatar shopping program is doing well. Today, it launched its Android app and went international, with markets in Canada and the UK.

What’s more important than the otherwise boring fact that it launched its Android app, however, is what’s happened to the company after going mobile. The company released its iOS app six months ago, and since then they say their monthly sales went from $200,000 a month to $3 million a month. Furthermore, 70 percent of their users now come through mobile instead of desktop.

So the question is: Why do people want to use an avatar-based social auction site on their phones more than on their computers? Does Tophatter’s traction tell us something bigger about a potential ecommerce model?

We hear a lot about how companies need to rethink their entire business operation for mobile, instead of merely grafting their website onto a phone. The best app companies harness the inherently different properties of smartphones — mobility, users being on-the-go, GPS, tactility, and speed — to build new types of experiences, whether with dating, gaming, or hotel booking. In dating, people now flip through faces without reading profiles, selecting or tossing romantic options in seconds. In hotel booking, people pick among a couple curated, excellent deals for same day sleeping, instead of searching painstakingly through listings in advance.

But how has mobile transformed shopping?

Some popular applications take advantage of mobile’s inherent properties. RedLaser and PriceGrabber let users scan product barcodes while shopping to see if they’re cheaper elsewhere. App Salesorter updates sales information in real time, showing users the best deals near them. Kaleidoscope collects item together in a pretty app “Window” for virtual window shopping.

But some of the most popular shopping sites, like eBay or Amazon, did not change that much when taken to mobile. Their apps are still stores, with buttons people click to surf through products before heading to check out. It’s still a slow, methodical process. User behavior is similar to desktop shopping because the apps haven’t capitalized on mobile’s unique properties.

Tophatter’s rapid traction after introducing a mobile app suggests that the company may be onto something when it comes to new ways people like to shop on their phone. Socially? Quickly? With limited product choices? With avatars? There’s a lot of elements of Tophatter that could be pulling in users.

“The members of our community look at Tophatter and engage with it in a way that more resembles a game than an online shopping site,” CEO Ashvin Kumar says. “The real time nature of the experience lends itself naturally to a mobile experience.”

In fact, the mobile version of Tophatter doesn’t even have a search function. Users can set a notification on their phone for when a particular item goes up for auction, but other than that the sales are mostly the result of customer serendipity. Tophatter’s not the sort of site where someone goes searching for a particular product they need to buy. Instead, users are more likely bid for whatever they come across, whenever they happen to log in.

Kumar says that users like Tophatter because it’s social meets shopping. “We make the shopping experience much closer to something you would do in the real world, which is frankly much more engaging and interesting than going to an Amazon page and clicking a buy button,” Kumar says.

Given that its revenue grew so much just by adding an iOS app and more than half of smartphone users are on Android these days, entrepreneurs building apps for ecommerce should pay attention to what happens with Tophatter after its new Android and international expansion.