Watermelon Seeds aren't the biggest threat any more.
We were all told as kids not to eat watermelon seeds. Each and everyone of us feared to having a juicy melon crawling out on a serpent-like vine out or mouths (or elsewhere), until we realized that there's enough acid in our stomaches to peel the paint of the Pentagon, not to mention cook a watermelon. The only bad part about that was we lost our excuse on why we were spitting seeds at our siblings. Then again, by that point we didn't care if we had one or not.
So you can imagine my concern when I stumbled across this little gem. A 28-year-old patient, Artyom Sidorkin, came to a hospital in the city of Izhevsk in Central Russia, complaining of chest pain and coughing of blood. After an x-ray, the doctors determined a tumor and feared it was cancer. They performed a biopsy, but when the tissue was removed they didn't find a tumor. Instead, they found the green needles of a fir tree.
“I blinked three times, and thought I was seeing things. Then I called the assistant to have a look,” says Vladimir Kamashev, doctor at the Udmurtian Cancer Center.
The branch measures 5 cm long. The bleeding was caused by the needles poking the capillaries. Sidorkin complained of pain, but never thought there was an alien body inside of him. The tree and lung have been preserved for further study, but Sidorkin is just relieved it isn't cancer. The 5 cm branch is obviously to big to have been inhaled, so doctors guess that Sidorkin must have inhaled a small or bud, which somehow took root and grew.
Stephen Colbert heard about this, and even gave it a segment on his show. And I must agree with him. This is the Craziest [Freaking] Thing I've ever heard. http://www.colbertnation.com/the-colbert-report-videos/225966/april-27-2009/craziest-f--king-thing-i-ve-ever-heard---fir-tree-lung