With 20 years, you're bound to forget a few "NCIS" guest stars. Welcome to MsMojo, and today we’re counting down our picks for well-known actors who have guest starred on the original “NCIS” - both before and after they became famous. Our countdown includes Billy Dee Williams, Eric Stonestreet, Lily Tomlin, and more! Are there any other stars who YOU think gave Gibbs and his team a run for their money? Sound off in the comments below?

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