I was passed by Bill Walton on a climb on the Tijuana/Ensenada ride, around 1980 I think. He was with the Clippers at the time but struggling with rehab from injuries. Big guy, big bike. He was just chugging along while seated, that easygoing pace Miguel Indurain had on climbs years later. I never could climb that easily.
Looks like his joints are really stiff, just watching the short distance he moved in that first video clip above.