Lessing was also seen in three episodes of the Western series The Virginian, including one with Parley Baer and another with John Anderson. Additionally, he appeared in two episodes of I Spy: one with Roy Jenson and Lawrence Montaigne in 1966, and another with Diana Muldaur and Kenneth Tobey. Lessing was last seen in a 1971 episode of The F.B.I., in which fellow TOS guest actor Stephen Brooks starred from 1965 to 1967. He is also an accomplished flamenco guitarist and taught guitar at Santa Monica College since the early '70s. He recently retired from his position.