On the 25th anniversary of “Licensed to Ill,” an oral history of the birth of the Beastie Boys. “Then we were like, ‘Oh, shit, we should get a D.J.! Like rap groups. They have a D.J.!’ Nick Cooper knew about this guy Rick Rubin who went to NYU and would throw parties and had turntables. And a bubble machine. We were like, ‘If we had a fucking D.J. and a fucking bubble machine, we’d be fucking killing it.’”