Despite only scheduling a 30-minute meeting, the pair spent 2 hours together forming the unlikely life-long friendship.
"The two became fast friends, and were known to have exchanged gifts with one another over the course of their friendship," the Sotheby catalogue notes read.
Williams was a passionate All Blacks fan and often wore a cap given to him by Lomu on one of his many visits to New Zealand.
Creating A Stage: The Collection of Marsha And Robin Williams, a remarkable Sotheby's auction that included autographed scripts, film props, street art by Banksy, Tour de France memorabilia and sculptures, auctioned 310 items to raise a total US$6,088,250 for the Muhammad Ali Foundation.