The line comes from Halo: Reach, the 2010 first-person shooter developed by Bungie for Xbox 360. Its multiplayer announcer, voiced by Jeff Steitzer, uses short stadium style calls to mark modes and match moments, and Play Ball is one of the briefest and most recognisable. As Halo clips spread through YouTube, streams and soundboards, the call escaped its original context and became a general start signal online. Its mix of sports language and sci-fi presentation is why creators still borrow it for competitions, challenges and match openings.