Well, not the entire cast, because two had died long before I started collecting autographed photos - George Reeves ('Clark Kent/Superman') in 1959 and John Hamilton ('Perry White') in 1958.
But, I did get signed photos from four other cast members: Phyllis Coates, Jack Larson, Noel Neill, and Robert Shayne.
Phyllis Coates was the first 'Lois Lane', during the first season of "Superman". This signed photo was obtained in person for me, by my friend Brad, at a special event in Monterey, California, in 1997.
Noel Neill was the second and most well-known 'Lois Lane'. She joined the series in 1953 and stayed until its end in 1958. While living in Los Angeles in the mid-1970s, I called her - she was listed in the telephone directory, and as I recall, she lived in Santa Monica. She was very cordial and we talked for several minutes, but when I asked for an autographed photo, she politely explained that she had an agreement with some show promoters (I think it was some convention people) that she would only sign photos sold at those shows. In 1982, when I was back in New York, I sent her this photo, and she did sign and return it promptly. Perhaps she did so because it was not a "Superman"-related photo.
Jack Larson played the role of 'Jimmy Olsen', the young reporter who was usually partnered with 'Lois Lane', from the first season right through the end. In 1982, I sent him this photo, which he signed and returned within a few weeks.
Robert Shayne was 'Inspector Henderson' from the first season through the end. He was a veteran actor whose credits extended back into the 1930s. In 1982, I called him after finding his number in the Northwestern Los Angeles suburban phone directory. Mr. Shayne was somewhat stand-offish during our brief conversation. He was probably tired of hearing from people who'd ask him questions about the death of George Reeves. I asked if it would be ok to send him a couple of photos to have autographed, and he said that would be ok, as long as I provided the return postage-paid envelope. I also asked if I could ask some questions in my letter, and his reply: "You can ask anything you want, but I don't have to answer". I thought it best to just send the photos, and leave out any questions. Mr. Shayne signed both photos and returned them promptly. One is a vintage portrait and the other is a scene still from "Superman". He signed both as 'Bob Shayne', as if we were old pals. Perhaps he felt some kind of affinity with me when he noticed my residence city of Mount Vernon, right next door to his old hometown of Yonkers.