The Mad Hatter is a character from Alice in Wonderland. He is best friends with the March Hare and is first seen in the most famous scene in the film, The Mad Tea Party.
The Mad Hatter was famously voiced by Ed Wynn in the original film.
The Mad Hatter is a resident of Wonderland and the best friend of the March Hare, as mentioned above. Together, the two commonly engage in tea parties; most of which are to celebrate their "unbirthdays". While the Hatter is loud, eccentric, and insane like the rest of Wonderland's residents, he's also rather charming, and can be mild-mannered from time to time, particularly when dealing with visitors such as Alice. According to Hatter, he and the March Hare never get compliments on their singing, and they're usually the only attendants at the frequent unbirthday parties, apparently making the duo outcasts in the realm of Wonderland. This is most likely due to their overbearing antics and personas, as well as the fact that they're both, especially the Mad Hatter, troublemakers, albeit innocently so. This could be seen when the Mad Hatter made an attempt to "fix" the White Rabbit's watch.