On what American TV series did William Shatner and Leonard Nimoy work together before “Star Trek”?

'The Man from U.N.C.L.E.' is an American television series that ran for three and a half seasons on NBC, from September 22, 1964 to January 15, 1968. It was cancelled mid-way through its fourth season. 105 episodes were produced, each with a 50-minute running time. Season One was filmed entirely in black and white, except for the pilot episode, "The Vulcan Affair," and "The Double Affair", which were filmed in color since they were planned to be turned into feature films.

Season 1 episode 9: "The Project Strigas Affair" was aired on November 24, 1964.

Solo and Kuryakin devise a scheme to discredit a Balkan diplomat. Kuryakin goes undercover as an operative from the diplomat’s home country sent to investigate the fictional ’Project Strigas’. This episode features William Shatner and Leonard Nimoy, shortly before they became the stars of "Star Trek". Peggy Ann Garner, Sheila MacRae and Werner Klemperer guest star.