Rebecca is a young girl that Sheldon Cooper unsuccessfully attempts to befriend in "The Friendship Contraction".
Biography
Sheldon decides to head to a bookstore to find literature on the subject of friendship. In the children's section he finds "Stu the Cockatoo is New at the Zoo." He tries to make friends with Rebecca, a little girl who also likes monkeys. He invites her to go with him sometime to see the monkeys; however, Leonard Hofstadter pulls him out before he gets arrested as a stalking pedophile.