He developed Electrical Porcelain with transmission engineers at GE. His family continued to work at Building 68 in Schenectady for decades. William's son Frank Cermak advanced insulator design into the mid 20th century.
When Rex Harrison accepted his Academy Award for My Fair Lady (1964), he dedicated it to his two fair ladies, Audrey Hepburn and Julie Andrews both who had played Eliza Doolittle with him.
Audrey Hepburn later admitted she would never have accepted the role of Eliza Dolittle if she had known that producer Jack L. Warner intended to have nearly all of her singing dubbed. After making 'My Fair Lady', Hepburn resolved not to appear in another film musical unless she could do the singing on her own.