Kim, Joyce
From The Big Bang Theory Wiki
Leonard once broke up with a girl named Joyce Kim, although it appears to have been not so much of a breakup as it was the result of her defection to North Korea. Their relationship lasted only 27 days (0209).
As it transpired, Joyce was in fact a North Korean spy who started a relationship with Leonard to learn more about the top secret rocket fuel he was working on. Sheldon inadvertently saved Leonard from giving away the secrets when he barged in on Leonard and Joyce as they were in bed (0322).
Joyce Kim is played by Ally Maki in the season three flashback episode (0322).
