Misjoinder

In legal procedure (both civil and criminal), misjoinder (also known as wrongful joinder) involves the improper inclusion of one or more parties or causes of action within a lawsuit. The two forms of misjoinder are:
 * Misjoinder of causes of action, or counts: joining several demands to enforce substantive rights of recovery that are distinct and contradictory.
 * Misjoinder of parties: joining as plaintiffs or defendants persons who have conflicting interests, or who were not involved in the same transaction or event.

United States
According to FRCP, Rule 21,