As long as there have been cameras, there have been photobombs, the term applied to pics where something unexpected -- and often embarrassing -- happens in the background of a shot.

But the rise of digital cameras in the last decade has made it so photos that would ordinarily be rejected are now kept and, if bizarre enough, enjoyed as the accidental "messterpieces" they are, according to unofficial photobomb historian Beverly Jenkins.

"I have one photobomb that dates back to 1880," Jenkins told The Huffington Post last November. "The term may be new, but I think it's been around since the first person held rabbit ears behind the head of someone."

Despite its rich history, photobombing is only now getting immortalized in a book, "Oddee Presents: Photobombed!: Making Bad Pictures Great and Good Pictures Awesomely Bad."

GALLERY: PHOTOBOMBS

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  • Photobombed!

  • Photobombed!

    Oddee.com, a website that has presented all sorts of odd things to its fervent readership since its inception in 2007, is writing a definitive book on "photobombs," the term applied to pics where something unexpected -- and often embarrassing -- happens.

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    Book author Beverly Jenkins combed through thousands of reader submissions and was especially interested in photobombs from weddings.

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    Jenkins says the best photobombs happen naturally, usually in inappropriate situations, which is why weddings are such a fertile source of material.

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    The term "photobomb" is only about 10 years old, but Jenkins believes the activity dates back since the invention of the camera, as this photo from 1880s demonstrates.

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    Jenkins says digital photography is responsible for the recent rash of photobombs because they let people save photos that would have been discarded in previous generations. Maybe for good reasons.

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    Some photobombs happen by accident, but Jenkins says there are some people who get a kick out of photobombing people who will have no idea what is happening until they see the picture.

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    Jenkins says the key to a good photobomb is that the people who are taking the photo have no idea what you're doing until it's too late. It doesn't take much. Just something that reflects your unique personality.

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    However, there are some photobombs that can't be planned -- even if you wanted to.

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    Celebrity photobombs are especially coveted by Jenkins, such as this one featuring 'That '70s Show' star Wilmer Valderrama, but she also wants ones where celebrities are doing the bombs. She says Michael Cera, Jake Gyllenhaal and Jack Black are famous photobombers.

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The book was compiled and written by Jenkins, with the help of readers of Oddee.com, a website that has presented all sorts of odd things since its inception in 2007.

Defining a photobomb can be as obtuse as the Supreme Court's definition of obscenity -- "I know it when I see it" -- but Jenkins said there are five things that are especially good at creating photobomb opportunities: Inserting oneself into a stranger's photo; weddings; parties; TVs in the background; and animals answering nature's call when the shot is being taken.

"It seems like photobombs happen all the time," Jenkins told The Huffington Post. "Everyone has one, even if they don't call it that."

READERS: SEND US YOUR PHOTOBOMBS! We're going to make a slideshow of HuffPost readers' photobombs. Send your best one to Andy.Campbell@HuffingtonPost.com by Friday, Sept. 7, and prepare to get photobomb famous. Keep it classy, folks.