According to the mathematical formula that Sheldon gives for predicting the length of Leonard's relationships, his date with Penny should have lasted four and a half hours rather than three. Furthermore, the formula only works if Leonard's first relationship (with Joyce Kim) counts as number 0 rather than number 1.
Stephanie confesses to Leonard that when she X-rayed a patient, she saw one of her earrings that had fallen into him during surgery. In fact, it is a strict rule for all staff attending an operation in any U.S. hospital to remove all jewelry, piercings etc. before entering the operating theatre.