The Big Bang Theory: 10 Best Characters Who Only Appeared In One Episode
6. Mrs. Latham (Jessica Walter)
Episode: "The Benefactor Factor" (Season 4, Episode 15)
Yet another character with an inexplicable attraction to Leonard!
Sheldon, Howard, Raj and Leonard are forced to attend a university fundraiser and suck up to rich donors. Leonard is surprised to find that one of the wealthy benefactors, Mrs. Latham (Jessica Walter), is interested in him romantically as well as professionally. How far will Leonard go for science?
Jessica Walter has well and truly mastered playing the role of a classy woman with a razor-sharp tongue and questionable morals. She's done it for years as Lucille Bluth in Arrested Development and Malory Archer in Archer - Mrs. Latham fits right within that wheelhouse. Not only is Walter (and her brutal one-liners) entertaining to watch, but her acting calibre lifts the game of all the other Big Bang crew. It's surely not a coincidence that this episode saw Johnny Galecki receive an Emmy nomination for playing Leonard.
Spoiler alert: Leonard does go all the way with Mrs. Latham, but it's a dire shame that she didn't go all the way to another episode.