Dr. Elizabeth Plimpton is an attractive cosmological physicist and nymphomaniac from Princeton University, who is under consideration for a position at the California Institute of Technology and comes to Pasadena as a friend and personal guest of Sheldon Cooper in "The Plimpton Stimulation". A leading expert on quantum cosmology, she wrote a book entitled "The Effervescent Universe". Leonard is a huge fan of her work and Sheldon thinks she is one of the great minds of the 21st century like himself.
At first she seems forgetful and a bit scatterbrained, though no more socially dysfunctional than Leonard and Sheldon. She quickly sizes up her male company because she is very sexually active, seducing Leonard within hours of meeting him. Later she attempts to seduce Rajesh Koothrappali, Howard, and Leonard for a four-way sexual encounter. An upset Raj provides an escape route from his apartment for Leonard and Howard, once they realize they don't want to see each other naked. After Leonard and Howard have gone, Raj locks the door behind him and accepts Dr. Plimpton's advances.
- She told Leonard that she wrote the section on the Wilson-Bappu effect in Chapter 6: "The Extragalactic Distance Ladder" of her book, The Effervescent Universe, completely naked. Whether this was true or simply a ploy to seduce Leonard is never revealed.
- Elizabeth Plimpton is an attractive scientist who looks like a supermodel.