The King of Hearts is a character from the book Alice's Adventures in Wonderland by Lewis Carroll. He seems to, when compared to the Queen of Hearts, be the moderate part of the Wonderland government. As an example, when the Queen, who enjoys ordering beheadings, attempts to have Alice executed (charged with being unable to answer who is lying down in front of her) the King of Hearts reminds her that she is only a child.
The King also quietly pardons many of the subjects the Queen has ordered to be beheaded when the Queen is not looking. This guarantees few people are actually beheaded. Nevertheless, when the Queen plays a game of croquet in the story, the only players who remain at the end are himself, the Queen, and Alice.
At the Knave of Hearts' trial, however, where he acts as judge, he is revealed to be quite juvenile, with such lines as, "don't be nervous or I'll have you executed on the spot" to the Mad Hatter, or asking the Duchess's cook irrelevant questions such as, "what are tarts made of?" Between the two of them, the King and Queen appear to present a fairly accurate portrayal of why Wonderland is as childish, reckless and confusing as it is.
The Disney movie portrays the King of Hearts as a dwarf wearing an extremely tall crown, who is very much subdued by the Queen in terms of popularity among their subjects. He also seems to be less bright than in the book: for instance, when he first sees Alice, he thinks she is another card. He also squeaks happily behind the subject being ordered beheaded, once the Queen gives the order, taunting the guards that are carrying away the subject to be beheaded, as if he had given the order himself.
He appears briefly when the Cheshire Cat entangles the Queen's croquet mallet (actually a live flamingo) in her dress, causing her to fall over and expose her underwear. The King then gives the order to save her modesty, which nearly all characters present do, with the sole exception of Alice. This causes the Queen to blame Alice for the embarrassing situation. Just as she orders Alice's head off, the King of Hearts requests a trial beforehand. This irritates the Queen, prompting the King to add that it will only be "a little trial". The Queen accepts; however, when the trial begins she offers an atypical approach towards justice: sentence before verdict (the same stance taken by her original portrayal in the book with regard to the Knave of Hearts).
The King again stops her, saying they should call witnesses first. The witnesses called are the Mad Hatter, March Hare, and Dormouse. The Cheshire Cat reappears and upsets the Dormouse, who briefly puts the court into disorder. The Queen again blames Alice for it, and orders her beheaded. At this, Alice eats mushrooms she had earlier procured, which make her grow bigger. Although the King announces rule #42, which says that "all persons more than a mile high must leave the court immediately", Alice feels free to call the Queen a "fat, pompous, bad-tempered old tyrant" while growing to her new size. The Queen gives the order a third time; as Alice flees, the King uses his oversized crown as a megaphone to tell the guards to "do as her Majesty says". He was voiced by Dink Trout in 1951 film and by Tony Pope in attraction.
In the 2010 movie, Alice in Wonderland (2010 film), the King of Hearts was revealed to have been decapitated by the Queen out of the fear that he would've left her for the White Queen if she hadn't done it.