So, why is a raven like a writing desk?
Originally the riddle had no answer, but Carroll made one up later. Many readers have invented their own answers ever since, including the most famous "because Poe wrote on both", and my personal favorite "because there's a B in both and an N in neither".
In a new preface that Carroll wrote for the 1896 edition of Alice, he gave what he considered to be the best answer to the Mad Hatter's riddle. This is what he wrote: "Enquiries have been so often addressed to me, as to whether any answer to the Hatter’s Riddle can be imagined, that I may as well put on record here what seems to me to be a fairly appropriate answer, viz: "Because it can produce a few notes, tho they are very flat; and it is nevar put with the wrong end in front!" This, however, is merely an afterthought; the Riddle as originally invented, had no answer at all. "Note the spelling of "never" as "nevar" (discovered by Denis Crutch). Carroll intended to spell "raven" backwards. The word was corrected to "never" in all later printings, perhaps by an editor who thought he had found a printer's error. Because Carroll died soon after this "correction" had destroyed the ingenuity of his answer, the original spelling was never restored. Whether Carroll was aware of the damage done to his clever answer is not known.
The Mad Hatter has a card on his hat which says '10/6'. What does it mean?
The card is a price tag in 'old' English money: pounds, shillings and pennies, which was then written as l/s/d. Lewis Carroll has explained the meaning of the tag in his Nursery Alice: The Hatter used to carry about hats to sell: and even the one that he's got on his head is meant to be sold. You see it's got its price marked on it - a "10" and a "6" - that means "ten shillings and sixpence." Ten shillings and six pennies (expressed in conversation as "Ten-and-Six") was quite a large sum in the mid-1800's. Chris Somerville emailed me and amplificated: The actual amount was significant also. Professional people (doctors, lawyers, architects etc) all charged fees, not in pounds but in guinneas. One guinnea was one pound plus one shilling. And while pounds were the currency of trade, guinneas were the currency of the professions. We used to have a gold coin called, and valued at a guinnea, and a smaller gold coin, a half guinnea, valued at ten and six (10/6). The pound, however was merely a paper note, as was the half-pound or ten shillings. So the hat worn by the Mad Hatter was priced at half-a-guinnea, signifying its superior style.
These and other fun facts can be found at Lenny's Alice in Wonderland site from which they were quoted.
The Mad Hatter Marionette has been made available for sale on Etsy.