Fun Fact 1: The Mad Hatter was featured in DC Comics, first seen in 1948, under the name of 'Jervis Tetch.' In the comics, he was made to portray another one of Batman's many enemies. The Mad Hatter even made it into the Batman television series, and a few different video games.
Fun Fact 2: The Mad Hatter is meant to be 1000 years old...
Fun Fact 3: In the original Disney version of Alice In Wonderland, The Mad Hatter was going to try to kill Alice with a giant pair of scissors! I'm kind of glad that Disney excluded that bit, considering not only my own childhood, but that of every other person who grew up watching Disney's Alice In Wonderland. Although I must admit, that would be kind of interesting to watch...
Fun Fact 4: The line "Why is a raven like a writing desk?" was used in the novel 'The Shining,' written by Stephen King.
Fun Fact 5: Lewis Carroll made another book called Alice Through The Looking Glass, which was later made into a Tim Burton movie as well. (I was going to do a section on this as well, but that could be a whole other site worth of information!)
Fun Fact 6: Several other Mad Hatter appearances include The television show 'Once Upon A Time,' The animated Netflix series 'Ever After High,' A short series created in 2009, A movie made in 1981, and several anime shows, where the Mad Hatter is often portrayed by a pre-existing anime character. (See the link titled 'Anime' above or below for examples of this.) Also, see the link titled 'Extra cool things' for links to a couple more sites, with extra facts. It is also shown above and below.