For over three decades and more than 1,000 episodes, Law & Order has been bringing gritty crime drama to viewers everywhere. Each version of the franchise, like the no-nonsense Law & Order, the sharper Law & Order: Criminal Intent, and the intense Law & Order: Special Victims Unit, offers its own unique style and energy.
With that came a range of memorable guest stars, too. From future A-listers early in their careers to established actors in surprising roles, Law & Order has a solid reputation for delivering unexpected celebrity cameos.
Let's look back at some of the most iconic Law & Order celeb appearances that you might've forgotten about over the years.
Scroll to see the Law & Ordercelebrity cameos you definitely forgot about...
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You may best know William H. Macy as drunken patriarch Frank Gallagher on Shameless or as the surprising voice of the narrator in Curious George. These two wildly different roles just go to show how diverse his talent is.
Still, you might not remember how William even made an early appearance on Law & Order in the very first episode of the series, playing Assistant US Attorney John McCormack in the pilot.
While this debut wasn't particularly memorable, he did get a second shot at redemption in Season 2. That time around, he played Jack Powell, the director of a teen shelter suspected of abuse.
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Everyone knows Amanda Seyfried for her breakout role as ditzy Karen Smith in Mean Girls. More recently, you might've seen her viral rendition of "California" by Joni Mitchell on The Tonight Show going viral across social media platforms.
However, she also appeared in a Law & Order: Special Victims Unit episode and played Tandi McCain, a teen girl who was found beaten and duct-taped under a bench in a new dormitory. This impactful performance couldn't have been a wider divergence from her Mean Girls character.
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Before Stephen Colbert became known for his sharp political commentary (and endless impersonations of Donald Trump), he also started off as an actor just trying to make it in Hollywood. One of his early TV roles came in 2004 when he appeared on Law & Order: Criminal Intent.
Stephen portrayed James Bennett, a counterfeiter whose actions threaten to ruin a Catholic charity. This role was far removed from his typical comedic persona and offered a rare glimpse at Stephen's darker acting abilities.
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Prior to becoming the heartthrob we all know and love today, Bradley Cooper was already proving he had the chops to play some seriously twisted characters. During a Law & Order appearance, he portrayed Jason Whitaker, a psychotic lawyer whose dark past catches up with him.
What makes Bradley's guest spot even more interesting is that it was part of a crossover event between Law & Order: Special Victims Unit and the spin-off Law & Order: Trial By Jury. His storyline begins on SVU and continues in the latter.
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Before John Krasinski became a household name for his role as Jim Halpert on The Office, he showcased his darker side on Law & Order: Criminal Intent. He played Jace Gleesing, a troubled high school basketball player suspected of murdering a private investigator.
Viewers got to see John act as a wildly different character than the lovable and quirky paper salesman he's most known for today.
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Robin Williams is remembered for his iconic roles in both comedy and drama and his performance in Law & Order: Special Victims Unit is no exception.
In the Season 9 episode "Authority," he portrayed Merritt Rook, a sound engineer turned anti-authoritarian criminal mastermind. Merritt is pushed to the edge after the tragic loss of his wife and unborn child, setting him on a path of revenge, and Robin's captivating performance even earned him an Emmy nomination.
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During the ninth season of Law & Order, Julia Roberts also made a memorable guest appearance. When a millionaire investor died shortly after backing a new sports stadium, the investigation hones in on a construction entrepreneur as the prime suspect.
Julia plays Katrina Ludlow, a professional fundraiser who claims to have uncovered evidence implicating the killer. There's just one catch: she insists on delivering the evidence to Detective Rey Curtis under a set of complicated circumstances.
The star earned an Emmy for this performance, adding another achievement to her impressive resume.
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Finally, Samuel L. Jackson made an early appearance on Law & Order during its very first season. He played lawyer Louis Taggert in the episode "The Violence of Summer," which aired before his famous role as Ray Arnold in Jurassic Park.
Samuel flexed his acting muscles with some classic scenes in the interrogation room, adding even more intensity to an already dramatic show.
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