Hollywood might be big business, but its also a very small town. So it's no surprise that some celebrities often get mixed up with one another. And here are the top 15 most frequently misidentified stars:

Matt Damon and Mark Wahlberg

These two BFFs couldn't be more alike; they both hail from Boston and are 42 year old action movie stars. They even made a pact to oblige eager fans by signing autographs as their doppelgangers.

Nelson Mandela and Morgan Freeman

There's a reason why Morgan Freeman was the obvious choice to play Mandela in the 2009 film, Invictus. After the famous South African politician's death in 2013, a photo of the actor's face incorrectly printed on a billboard meant to memorialize the deceased icon blew up on Twitter.

Glenn Close and Meryl Streep

Both icons are the most prestigious and well-respected actresses in Hollywood, and there have been rumors that they've had to fight it out to win roles. But these doppelgangers keep their catfights classy: Meryl was even quoted saying, "On behalf of Glenn Close and me, who are often mistaken for each other, there should be no illusions… I adore her."

Kevin Spacey and John Cusack

During one unfortunate interview, a college student mistakenly thought Cusack was the star of American Beauty, when it was actually Spacey who won a Best Actor Academy Award for the role of Lester Burnham.

Chace Crawford and Ian Somerhalder

The reason these teen heartthrobs get mistaken for each other has to do with their chiseled features, piercing baby blues, sky-high cheekbones and tousled hair:

Keira Knightley and Natalie Portman

Knightley once stood in as a double for Portman in Star Wars, and she hasn't lived it down since. Knightley has recounted many stories of being chased down in airports while being called Natalie the entire time. 

Timothy Olyphant and Josh Duhamel

According to Duhamel, he often gets mistaken for other celebs, including Olyphant (star of The Crazies), Jackass’s Johnny Knoxville, and even Ryan Seacrest.

Erika Christensen and Julia Stiles

With their feminine features and curly blonde hair, there's simply no denying that these two highly respected actresses do bear an uncanny resemblance to each other.

Michelle Williams and Carey Mulligan

For her role in The Great Gatsby, Milligan got a pixie haircut which was almost uncanny to Williams' trademark pixie hairdo.

Mila Kunis and Sarah Hyland

Both might have started out their careers during their teens, but that's about the only thing they have in common. Kunis is best known as the "lovable but steamy starlet" through her roles in Forgetting Sarah Marshall and Black Swan; while Hyland's image is more wholesome thanks to her roles in Disney movies and Modern Family.

Jeffrey Dean Morgan and Javier Bardem

Morgan couldn’t be more different than the Spanish born Bardem, but you have to admit that they could still pass off as each other's stunt-doubles.

Michael Cera and Jesse Eisenberg

Both are known for their "awkward," offbeat roles, so it's understandable that they often get mixed up for one another.

Dafoe and Denis Leary

Despite decades of being in the business, these two veteran actors still have to deal with celebrity mix-ups. According to Leary, he was once allowed inside a strip club for free simply because the bouncer thought he was "the guy from Spiderman."

Chad Smith and Will Ferrell

During a reddit AMA, Ferrell joked that they were both actually the same person. They famously acknowledged their uncanny resemblance after appearing on Jimmy Fallon’s The Tonight Show in a drum-off.

Zoe Saldana and Thandie Newton

Despite appearing in massive blockbuster hits, Saldana still gets mistaken with other celebrities, particularly Pursuit of Happyness star Thandie Newton and Scandal star Kerry Washington.