Stealing peoples songs is a big no-no in the music industry, don't even come close to something similar, and if you do, you better give credit where credit is due. This may haunt Nicki Minaj for years in royalties and credibility.
Katy Perry is known for her ever-changing hair. It was a no brainer when British hair care company GHD hired her as a spokesmodel, but things have soured between the parties and they are embroiled in a "They said, she said" contract dispute, with GHD suing the singer.
Dj/Producer Baauer never thought his song "Harlem Shake" would blow up the way it has with the aid of youtube but now that it has I bet he never thought he'd be getting sued for it either..