Ever hear the theory that everyone has a twin? Some believe that each and every person has a double somewhere on Earth. Whether that theory is true is debatable. However, it's uncanny how some celebrities resemble each other. Sometimes it's an obvious trait: similar hairstyle, body type or facial features. Other times it's more subtle: similar roles or names.

Whatever the reason, the following stars have something about them that makes them look like another famous somebody. And that's not always a good thing.

1.) Perhaps it's the enormous beer gut that makes this trio seem related.

Comic Book Guy From "The Simpsons," filmmaker Michael Moore & actor/writer Bruce Vilanch

2.) These three have to be the same person. Seriously. And are bangs in right now?

Actress Zooey Deschanel, pop star Katy Perry & "Pushing Daisies" star Anna Friel

3.) Once again, it's gotta be the bangs that make these two look like sisters.

Actresses Selma Blair & Michelle Monaghan

4.) Okay, so maybe they don't look exactly alike, but they are both equally annoying.

Actor Andy Dick & comedienne Kathy Griffin

5.) Dark hair and dark eyes, as well as similar choices in film roles, make these two actors very similar.

Actors John Cusack & Ron Livingston

6.) America the beautiful, or should we say Jordin the beautiful? It's creepy how similar these two look. They could be the same person. Sort of like Michael, Janet & LaToya Jackson.

Actress America Ferrera & "American Idol" winner Jordin Sparks

7.) These two actresses even dye their naturally brown locks the same color!

Actresses Anna Paquin & Thora Birch

8.) Leelee and Helen...a huge age difference (26 vs. 45), but they resemble each other in some weird way.

Actresses Leelee Sobieski & Helen Hunt

9.) That 70's gal Mila and high school cutie Vanessa certainly could be sisters. Wowzers.

Actresses Mila Kunis and Vanessa Anne Hudgens

10.) Nope. These two are not the same person.

Actresses Idina Menzel and Penelope Cruz

11.) Bald is beautiful.

Actors Vin Diesel and Dorian Gregory

12.) One's an actor, and the other is an actor wannabe.

Britney's ex Kevin Federline and actor Eric Balfour

13.) They have the same first name. They share initials. They do the same roles. They're easy to mix up!

Actors Bill Pullman & Bill Paxton

14.) These two are both hot in our opinion. Double the pleasure.

Actresses Bridget Moynahan & Rhona Mitra