The badges on the mess jackets worn by Darling and Melchett during their meal indicate they were both in the Foot Guards. Darling's features the badge of the Coldstream Guards; Melchett's is less clear but appears to be the Scots Guards.
Captain Cook remains the only episode over the entire four series run that only features the primary cast and does not feature any guest stars.
General Melchett tells the Lieutenant that his uncle Bertie sends his regards and asks for him to have a week off in April to attend the boat races. Hugh Laurie plays Bertie Wooster in the TV series Jeeves and Wooster (1990), and Stephen Fry plays his valet, Jeeves. Hugh Laurie was also on the rowing team at Cambridge which not only refers to the request to have him attend the boat races, but to Laurie and Fry's hand-clapping game about rowing.