I had the same thought when Louisville was mentioned as part of the clue, but thought ... probably not. Good for Jon for knowing the Louisville Lip.
In thinking of celebrities from Riverside, I only come up with basketball players Cheryl & Reggie Miller along with baseball player Bobby Bonds (father of Barry), singers Little Richard and R&B singer Etta James. All combined, they don't even come close to the fame of Muhammad Ali.
Oh, and there was swimmer Cynthia Woodhead, predicted to win 6 gold medals in the 1980 Olympic Games that President Carter chose to boycott. I've have never forgiven him for that.http://www.ishof.org/Honorees/94/94cwoodhead.html