Imagine the day when TV commercials will sport ‘buy’ buttons allowing you to purchase products on the spot if you like the ad. Scary? Well that day is here, and the first such ad to air nationally in the U.S. is aimed at kids.

Last month, New York-based Ammirati Puris Lintas launched Disco, a new U.S. national 30-second spot for Lego Mindstorms. Produced by U.K.-based Aardman Animations, it features droids dancing under a disco ball and is designed to show off the possibilities offered by the Lego Mindstorms Droid Development Kit. Those watching the ad on a regular TV see it like any other spot, but those with the Microsoft WebTV Network Plus service see a stylized ‘I’ in the top right-hand corner indicating that the ad is interactive. A click of the WebTV remote brings up a host of options, including a button taking the viewer to Lego’s WorldShop on-line store.

The interactive elements were added to Ammirati’s spot in post by APL Digital, the agency’s interactive arm.

Ammirati also launched a similar interactive ad for Thomson Consumer Electronics’ RCA HDTVs in late November.