Spoiler Warning: The following article contains SPOILERS for Harley Quinn season 3.
Content Warning: the following article contains discussions of sexual violence.
The horrific version of the Mad Hatter presented in Harley Quinn season 3 invites comparison to the more light-hearted versions of the character from the comics and other cartoons. Every adaptation of the Mad Hatter tends to be somewhat unsettling, due to his appearance and the potential for perversion inherent in his mind control powers. Yet the Jervis Tetch of Harley Quinn proves even more unsettling, due to a notable shift Mad Hatter's in how he enacts his plans.
The action of Harley Quinn season 3, episode 7, "Another Sharkley Adventure" centers around an unlikely team-up between Harley Quinn and Batgirl (Barbara Gordon), after both women are abducted by the Mad Hatter. Tetch boasts that thanks to his latest scheme, marketing hats that place people under his control as a high-end fashion accessory to Gotham City's wealthy elite, he will soon have an army of people "to fool around with." When Harley comments that the last thing Gotham needs is another "run-of-the-mill perv," Tetch protests that he only uses his mind control powers for "torture and murder - nothing gross!" The fact that he explains this while invading Batgirl's personal space and sniffing Harley's hair does not help his case, nor does his cleaning his ear with an incredibly long pinky nail. This appears to be what is commonly known as a coke-nail, as some cocaine users grow one fingernail longer than the others to make it easier to snort cocaine.
Disturbing as this detail is and the direct connection between Mad Hatter and hard drugs, it is also a sly reference to Mad Hatter's altered origins in the New 52 DC Comics Universe, where Tetch suffered from a medical condition that slowed his physical maturity. He turned to experimental drugs in the hopes of enhancing his height, but the drugs ironically left him unable to mature emotionally, causing him to lose his grip on reality and become convinced that he really was the Mad Hatter character he came to resemble. He turned to psychedelic drugs to gain glimpses of Wonderland, and it is hinted that Harley Quinn's Mad Hatter may have taken things one step further.
Harley Quinn's Mad Hatter Detail Doubles Down On The Darker Comics
Harley Quinn's take on the Mad Hatter also seems to borrow a bit from Batman: Madness. Originally published in the Batman anthology comic Legends of the Dark Knight and created by writer Jeph Loeb and artist Tim Sale before they produced Batman: The Long Halloween, Madness detailed Batman and Commissioner Gordon's efforts to rescue Barbara Gordon and several other missing children, who were kidnaped by the Mad Hatter and drugged into acting like characters from Alice in Wonderland. The story implied that this version of Jervis Tetch was a child molester, with Batman thinking about how "children should be allowed to dress up as spooks and fairies and collect candy... without having to worry about being poisoned... molested... or worse..." as he fought the Mad Hatter. Batman also noted that not even Joker disturbed him as much as the Mad Hatter.
This was easily the darkest take on the Mad Hatter ever presented in the comics. It should be noted, however, that despite the implications of what someone could do with mind control technology, most versions of the Mad Hatter are comedic figures who favor hypnotism to hypodermics full of mind-altering substances. Even the Mad Hatter of Batman: The Animated Series was presented as a funny little man with a Lewis Carroll fixation after his origin story established him as a jilted stalker with a murderous obsession with a woman named Alice. Despite this, the Mad Hatter of Harley Quinn is easily the darkest, most disturbed version of the character ever presented in animation, and in the running for the darkest in any medium, making his sudden death at Harley Quinn's hands potentially understandable.