Are you a fan of NCIS? Having been on screens for nearly two decades, the show has seen plenty of cast members come and go over the years.
But as well as the main cast, many famous faces have popped up in the show over the years - some before they were even famous! For all the celebrity cameos you might have forgotten about, click through the gallery to take a look...
WATCH: NCIS star opens up about his favourite memories on set
Before becoming the heartthrob he is today, a then 19-year-old Zac Efron appeared in the CBS drama in a season three episode. The episode aired just months before High School Musical premiered on Disney, propelling the young actor to superstardom.
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Millie Bobby Brown
Stranger Things actress Millie Bobby Brown appeared in NCIS in what was one of her first on-screen roles. In the season twelve episode, she played Rachel, the daughter of a young psychologist who was murdered. While the team launched an investigation into who could have committed the crime, the team soon found out there was a dark side to this little girl.
Tom Hanks' eldest son, Colin Hanks appeared in three episodes of the CBS drama across season ten and 11 playing Inspector Parsons. While he initially clashed heads with Gibbs, he soon had a change of heart after witnessing him in action during a life-saving operation.
In 2016, NCIS became the first show to be filmed in the White House - and even bagged an incredible cameo at the same time! The then-First Lady Michelle Obama appeared in the show's thirteenth season to promote her organisations supporting veterans, active military, and their families.
Talking about her acting debut on the show, Michelle said: "It's a great way to incorporate our military families and make more Americans aware of the challenges they face."
Jamie Lee Curtis
Jamie Lee Curtis appeared in the show as Gibb's girlfriend, Samantha back in 2012. She appeared in five episodes before her scary ex was released from prison, causing her to skip town, leaving our special agent heartbroken.
Actress Abigail Breslin appeared in the season two premiere as a play blind pianist who gets kidnapped. Later in the episode, we learned her captor was someone she knew.
Lily Tomlin made an appearance in the police drama as Penelope Langston, Timothy McGee's ex-hippie grandmother, a role not so different from her current turn as Frankie in Grace and Frankie.
Lord of the Rings and Stranger Things star Sean Astin played a tough-willed investigator in series nine of the show.
Sterling K. Brown
Before starring in This Is Us, Sterling K. Brown appeared on NCIS playing a killer clown. In the terrifying episode, he kidnaps Diane Sterling, Gibbs' ex-wife, and her daughter.