Mylan Laboratories, Inc. v. Blue Cross Blue Shield of Massachusetts

Issue: (1) May diversity jurisdiction be created retroactively after a trial when the plaintiffs’ citizenship was never pleaded or proven? (2) Whether the exception for a "jurisdictional spoiler" recognized in Newman-Green, Inc. v. Alfonzo-Larrain, permits a court to sever numerous nondiverse parties who are also real parties in interest .