Jennifer Lopez  donned a nude-colored gown to attend Muhammad Ali's Celebrity Fight Night in Phoenix, AZ, last night. She had boyfriend Casper Smart by her side for the annual event that benefits the Muhammad Ali Parkinson Center as well as other charities. Jennifer, who also brought her sister Leslie Lopez along, wasn't just one of the star-studded crowd: she took the stage to give a live performance, which included a duet with Andrea Bocelli. She also linked up with the host of the evening, Ali, at the event that brought out Rita Wilson, Steve Martin , and more. J Lo traveled to the desert for the Fight Night with Casper after getting in quality time with her twins last weekend in LA.