In an effort to find an innovative way to encourage tweeting at AT&T-sponsored events, Team Epic worked with Brightline Interactive to develop what it calls a “Twitter balloon”: a balloon six feet in diameter connected to an air compressor that is activated by tweets with a particular hashtag. “There are a lot of Twitter walls that show tweets as they come in, but this performs a physical action and it happens within less than a second,” said Andrew Knutson, manager for Team Epic. “As soon as you tweet, you hear the air going to the balloon, which is pretty cool. You’ll see crowds forming, especially as the balloon gets bigger.” AT&T unveiled the balloon at the N.C.A.A. Final Four men's basketball championship last spring and has since used it at events such as the Outside Lands Music & Arts Festival in San Francisco, the College World Series in Omaha, CMA Music Festival in Nashville, and Music Midtown in Atlanta. Signage at the events encourages attendees to tweet with a particular hashtag. Each tweet triggers a burst of air into the balloon, and the person whose tweet causes the balloon to pop wins a prize such as an AT&T phone.