Here's singer Demi Lovato's episode of Grey's Anatomy explained. It's doubtful anyone involved with Grey's Anatomy knew that when the series debuted in 2005
The medical drama focuses on Dr. Meredith Grey (Ellen Pompeo), and the show has charted her journey from intern to Chief of General Surgery in Seattle Grace Hospital.
Outside of Grey's personal and professional life, Grey's Anatomy also revolves around the other doctors, surgeons and interns at the hospital, many of whom are hopelessly intertwined.
Over the years, Grey's Anatomy's ensemble has featured Patrick Dempsey, Katherine Heigl, Sandra Oh - who originally auditioned for another character - and many more.
Given how long the series has been running, it's little wonder that many pre-fame actors have played guest roles on the show.
Stranger Things star Millie Bobby Brown played a key role in Grey's Anatomy season 11 episode "I Feel The Earth Move," Thor: Ragnarok star Tessa Thompson
Lovato hasn't done much in the way of acting since their Grey's Anatomy guest role, though in recent years the singer cameoed in comedy Eurovision Song Contest: The Story of Fire Saga
playing elderly patients reconnecting after missing a chance at romance decades before. This subplot formed arguably the most moving of the episode.