The Outlier Pattern is designed to prevent a few queries or documents from driving an application's solution towards one that would not be optimal for the majority of use cases. It involves adding a field to flag documents as outliers, allowing the application to handle them slightly differently, and leveraging MongoDB's flexible data model to optimize performance for typical documents or queries. This pattern is often used in situations where popularity is a factor, such as social network relationships, book sales, movie reviews, and video conferencing events, where large lists of attendees can be expected. The Outlier Pattern requires consideration of ad hoc queries and potential code maintenance over time.