Cosplay attendees in his costume, as the Mad Hatter.
The Queen of Hearts and the Mad Hatter are character from the book Alice's Adventures in Wonderland by the writer Lewis Carroll.
The Queen is the primary antagonist. She is a foul-tempered monarch whom Carroll himself describes as "a blind fury", and who is quick to give death sentences at the slightest offense. One of her most famous lines she states often is "Off with their heads!"
Cosplay, a contraction of the words costume play, is a performance art in which participants called cosplayers wear costumes and fashion accessories to represent a specific character.