Stefani appeared as a coach on The Voice's seventh season. Usher sat in one of the four big red chairs for Season 4 in 2013 and Season 6 in 2014. Usher's artist Josh Kaufman actually won the reality singing competition's sixth edition.
Green was a coach on The Voice's inaugural season in Spring 2011 and stayed with the series through the end of its third edition. He came back for Season 5 but hasn't had anything to do with the show since. In fact, Green had announced in February 2014 he was leaving The Voice for good and never coming back.
Green disclosed his exit prematurely, so fans speculated there might've been a falling out. Around that time, the singer was facing a criminal charge of furnishing a controlled substance to a woman at a restaurant. Green accepted a plea deal in August of last year in which he pleaded no contest.
The Voice is produced by United Artists Media Group, Talpa Media USA Inc. and Warner Horizon Television. John de Mol, Mark Burnett, Audrey Morrissey, Marc Jansen and Lee Metzger serve as executive producers.