Tomacco
Tomacco is originally a fictional hybrid fruit that is half tomato and half tobacco, from the 1999 episode "E-I-E-I-(Annoyed Grunt)" of The Simpsons; the method used to create the tomacco in the episode is fictional.  The tomacco became real when it was produced in 2003.  The tomacco is one of the few made-up words in The Simpsons that resulted in real life application.

# Fictional tomacco
In the Simpsons' episode, the tomacco was accidentally created by Homer Simpson when he "planted a little bit of everything" and fertilized his tomato and tobacco fields with plutonium.  The result is a tomato that apparently has a dried, gray tobacco center, and, although being described as tasting terrible by many characters (Ralph Wiggum: "Eww, Daddy, this tastes like Grandma!" Clancy Wiggum: "My god, it DOES taste like Grandma!"), is also immediately and powerfully addictive. The creation is promptly labeled "Tomacco" by Homer and sold in large quantities to unsuspecting passers by. Laramie cigarettes, seeing an opportunity to sell their products to children legally, offers to buy the rights to market tomacco for $150 million. Homer refuses, demanding $150 billion instead. This offer is rejected by the company's executives. The hybrid plant is so powerfully addictive that farm animals develop the abilities of speech and bipedal locomotion in their frenzied quest to gain more tomacco.  A cow kicks through the wall of the Simpson farmhouse and screams a rudimentary "TOMACCO!" when looking for more. Eventually, all but one of the tomacco plants are eaten by farm animals. The company executives manage to steal the last tomacco plant as they depart, but a tomacco-crazed sheep attacks them, causing their helicopter to crash, destroying the last remaining plant. The sheep was somehow able to survive the crash.

# Real tomacco
In 2003, inspired by The Simpsons, Rob Baur of Lake Oswego, Oregon successfully grafted a tomato plant onto the roots of a tobacco plant. This was possible because both plants come from the same family, Solanaceae or nightshade, and furthermore both plants are dicotyledons (it is not possible to graft monocotyledons, because the xylem and the phloem are distributed in bundles throughout the stem, and therefore it is impossible to align the vascular tissues of the two plants).
The plant produced fruit that looked like a normal tomato, but Baur suspected that it contained a lethal amount of nicotine and thus would be inedible.  Testing later proved that the leaves of the plant contained some nicotine.  The world's first tomacco fruit, destroyed in the testing process, contained no nicotine.  The second tomacco fruit was given to a Simpsons writer.  The third was sold on eBay and the fourth was eaten by a Xerox engineer who suffered no apparent ill effects from the fruit.  The Tomacco plant bore fruit until it died  due to weather-related causes at the ripe age of 18 months, having spent the previous winter indoors.
The process of making tomacco was first revealed in a 1959 Scientific American article, which stated that nicotine could be found in the tomato plant after grafting. Due to the academic and industrial importance of this breakthrough process, this article was reprinted in a 1968 Scientific American compilation, Bio-Organic Chemistry, on page 170. (ISBN 0-7167-0974-0)
The 2004 convention of the American Dialect Society named tomacco as the new word "least likely to succeed." Tomacco was www.wordspy.com "word of the Day".