THE ONGOING CLASSIC FILM STRING CHALLENGE!!

Well, that's the thing.  I'm not sure I'm sure, but it sounds like something more involved than a list.  Look at his example:

Margaret Lockwood played
NELL GWYN, who was played by
Anna Neagle, who played
QUEEN VICTORIA, who was played by
Judi Dench, who played
QUEEN ELIZABETH I, who was played by
Cate Blachett etc etc

So, adding to that string, you could go:

Cate Blachett, who played
Maid Marian (assuming she was real), who was played by
Olivia de Havilland, who played
Charlotte Bronte, who was played by
Marie-France Pisier