Leopold is a construct Sheldon creates as part of an exquisitely convoluted, "un-unravelable" web designed to replace a ruse concocted by Leonard that Sheldon deems laughably transparent. After Leonard deceitfully told Penny that he couldn't come to her performance in a one night showcase production of Rent (musical) because Sheldon and him were attending a symposium on molecular positronium given by Dr. Emil Farman-Farmaian, Sheldon conceives a new lie in which he tells Penny that Leonard was untruthful because he wants to protect Sheldon from the embarrassment of having a drug addled cousin "Leopold" and that they are actually going to participate in Leopold’s drug intervention in Long Beach, California to convince him to return to rehab.