Do you know why is a raven like a writing-desk?

The Hatter opened his eyes very wide on hearing this; but all he said was, `Why is a raven like a writing-desk?'
`Come, we shall have some fun now!' thought Alice. `I'm glad they've begun asking riddles.--I believe I can guess that,' she added aloud.
`Do you mean that you think you can find out the answer to it?' said the March Hare.
`Exactly so,' said Alice.
`Then you should say what you mean,' the March Hare went on.
`I do,' Alice hastily replied; `at least--at least I mean what I say--that's the same thing, you know.'
<…>
`Have you guessed the riddle yet?' the Hatter said, turning to Alice again.
`No, I give it up,' Alice replied: `what's the answer?'
`I haven't the slightest idea,' said the Hatter.
`Nor I,' said the March Hare.
Alice sighed wearily. `I think you might do something better with the time,' she said, `than waste it in asking riddles that have no answers.'
Lewis Carroll. Alice's Adventures in Wonderland


Alice does not know “Why is a raven like a writing-desk”. What about you?

What have hobbit Bilbo Baggins and the largest sattelite in the Solar system got in common?

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What have hobbit Bilbo Baggins and the largest sattelite in the
Solar system got in common?
What is image annotation?

The Lord of the Rings became immensely popular in the 1960s and has remained so ever since, ranking as one of the most popular works of fiction of the twentieth century, judged by both sales and reader surveys. [...]
But how many people know the answer to the question above? What about raven and writing-desk?

Several tagged pictures can help you to find answer to one of the "riddles that have no answers.'

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Several tagged pictures (see What is image annotation?) can help you
to find answer to one of the \"riddles that have no answers\"

The Rabbit room at the back of the "The Eagle and Child"

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The Rabbit room at the back of the \"The Eagle and Child\" pub
Tolkien\'s Hobbit [...] and The Lord of the Rings [...] were first read to the Inklings [...]

J.R.R. Tolkien, C._S._Lewis and C.Wiliams [...]
and other friends met every Tuesday in 'The Eagle and Child' pub.
Do you remember 'The Eagle and Child' pub board?
The advetntures of the brave Hobbit (as small as a child) who was carried by the Eagle were first read at the Rabbit (compare "hobbit") room at the back of the "The Eagle and Child" pub.
Brief quotation
"He wondered what other nonsense he had been saying, and if the eagle would think it rude. You ought not to be rude to an eagle, when you are only the size of a hobbit, and are up in his eyrie at night!"

The "Eagle and the Child" board

You expect me to tell you who is the poor child? His name is Ganymede .

Zeus assume his own eagle to transport Ganymede to Mount Olympus

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Jupiter (Zeus) assume his own eagle to transport Ganymede to Mount Olympus. That's why...

Ganymede was kidnapped by Apollo from Mount Ida in Phrygia, the setting for more than one myth-element bearing on the early mythic history of Troy. Ganymede was there, passing the time of exile many heros undergo in their youth, by tending a flock of sheep or, alternatively, during the chthonic or rustic aspect of his education, while gathering among his friends and tutors. Zeus saw him and fell in love with him instantly, either sending an eagle or assuming his own eagle nature to transport Ganymede to Mount Olympus.

More about Ganymede...

Among the more famous artists who depicted Ganymede are Leochares [...]
Michelangelo [...], Rembrandt [...], Correggio [...] , Peruzzi [...], Rubens [...] . In art Ganymede is most often depicted with the eagle like on the "Eagle and Child" Board.
Jupiter assume his own eagle to transport Ganymede to Mount Olympus. That's why...

JUPITER'S LARGEST MOON CALLED GANYMEDE...

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JUPITER\'S LARGEST MOON CALLED GANYMEDE...
Jupiter is the solar system's largest planet. Ganymede, one of the four Galilean moons of Jupiter, is the largest moon in the Solar System. It is larger than planets Mercury and Pluto.
For more details about Ganymede visit other my blog: http://nasaphotofan.blogspot.com/ [...]
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Now you can answer "What have Bilbo Baggins and is the largest moon in the Solar System have got in Common".
The Answer is "Ganymede myth"
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Sources:
Shippey, T. A. (2000). J. R. R. Tolkien — Author of the Century, Boston, New York: Houghton Mifflin Company.
Wikipedia: [...]
Nasa website: [...]
The Lord of the Rings official site [...]