Miss Young: This may have been Miss Isabella Young (1740/41?-1791), who earlier had played Titania in The Fairies.
Mr. [Charles] Blakes: Blakes was known for farce, pantomime, and his comic characters. He died in May of 1763, so his name does not appear in the final printed cast list for the November 1763 performance.
Miss Pope: Perhaps Miss Jane Pope (1744-1818), a full member of the Drury Lane company from 1759 through 1807, whose over fifty-year career was one of the longest running of the 18th-century English stage.
Mr. Vernon: Joseph Vernon (ca. 1738-1782), known both for his singing voice as well as his acting. Vernon was hissed off the Drury Lane stage on multiple occasions in his career due to his testimony against his own wife in a scandalous court case.