CNN's kaitlancollins talks to music legend Willie Nelson about a surprising memory from a 1979 White House visit with President Jimmy Carter's son. Nelson is set to perform this weekend at the 40th annual Farm Aid festival, along with Neil Young, John Mellencamp, Dave Matthews and more. "Farm Aid 40" airs live on Saturday, September 20 at 7p ET on CNN. #willienelson #farmaid2025