Kid Cudi took to the witness stand on Thursday to testify at Sean 'Diddy' Combs' sex-trafficking trial. Cassie alleged that Diddy reacted violently when she and Kid Cudi had a fling in 2011.

Amid her on-and-off relationship with Diddy, Cassie had a brief romance with Kid Cudi. Here's everything to know about Cassie's relationship with Kid Cudi, including why he is now testifying at Diddy's sex-trafficking trial.

Sean Combs’ trial continues to unfold in New York, with some high-profile individuals finding themselves in the mix due to taking the witness stand. One of the latest stars to become embroiled in the case is rapper Kid Cudi,