Martha

Martha is a Caltech student who seemed to be very interested in Sheldon. She is good friends with Abby and first appears in The Psychic Vortex.

Character Appearance
As Leonard and Howard are both off on a double date with Penny and Bernadette, Raj  feels lonely, and suggests to Sheldon  that they go out and have some fun. After much persuasion and actually giving away his Green Lantern lantern, Sheldon agrees to go with Raj. At the University Mixer, they meet Abby and Martha, where Martha instantly became interested in Sheldon's limited edition Green Lantern lantern and power ring. All four of them head back to Sheldon's apartment, where they are seen playing Guitar Hero (presumably). Raj yet again is interested in going out with Abby, but she will only agree to hang out with him if Martha can come along. Raj bribes Sheldon with his Incredible Hulk hands signed by Stan Lee. Martha and Sheldon engage in conversation, where she reveals her interest in Edwin Abbott's novella Flatland. As Sheldon states it's getting late and he has to go to bed, it is seen Martha suspects that she has to go with him. Sheldon shocks her by saying "Goodnight puny human!".

As Abby and Raj are getting busy in the living room, Martha makes her escape to Sheldon's bedroom, asking if she could hang out there for a while. Sheldon accepts, and immediately after says "I'll go sleep in Leonard's room".