When stage performers are heckled, they have two choices: ignore the heckler, or address the comment and work it into the conversation. The essential thing is to get the conversation (or performance) back on track without losing your focus. Hopefully, you don't get heckled often in business, but interruptions happen. In an interview, it's important to acknowledge questions or comments that come up. By practicing in a mock interview before-hand, you'll be prepared to address questions and be able to move the conversation along.