DC Universe's Harley Quinn series has a brilliant easter egg that nods directly to Adam West's classic version of Batman. Following in the footsteps of Young Justice: Outsiders, the streaming service greenlit a new animated series based on the titular anti-heroine. Developed by Justin Halpern, Patrick Schumacker, and Dean Lorey, Harley Quinn season 1 debuted in November 2019 to critical acclaim. It was rapidly renewed for a second season, which began airing episodes in April 2020, exploring the journey of Harley Quinn (Kaley Cuoco) as she tries to establish herself out from beneath the shadow of The Joker.
Created by William Dozier, the Batman series debuted via ABC and ran for 120 episodes across 3 seasons. Knowingly campy and tongue-in-cheek, the series starred West as Bruce Wayne and Batman alongside Burt Ward as his sidekick, Robin. Together they faced down a coterie of recognizable villains - including Cesar Romero as The Joker, Frank Gorshin as The Riddler, and Burgess Meredith as The Penguin. The 1960's Batman series also spawned cult favorite film in 1966. With the actors from the TV show largely reprising their roles, the film featured several iconic scenes that have remained in fans' consciousness to this day.
It was with this particular film - and one of those scenes - that Harley Quinn officially crossed streams. While on a ladder attached to the Batcopter, Batman is briefly lowered into the ocean. When he is lifted out of it again, a shark is revealed to have clamped down on his leg. Batman is finally able to free himself of its grip when Robin hands him a special can of Shark Repellent. In Harley Quinn season 2, episode 12, "Lovers' Quarrel", Harley recruited the newly released members of the Justice League to help bring down the traitorous Doctor Psycho. Along the way, Superman, Wonder Woman, and Batman clashed with brainwashed members of Harley's criminal crew - including Poison Ivy, Clayface, and King Shark. While battling the latter, Harley Quinn's version of Batman pulled a similarly labeled can from his utility belt.
This actually wasn't the first time the weaponized spray made an appearance on the show. During Harley Quinn season 1, episode 4, "Finding Mr. Right", Harley found herself stuck with Damian Wayne's Robin for a nemesis. In an effort to expose Damian as a liar, Harley threatened him with King Shark on live television. Unfortunately, the scent of blood sent King Shark into a murderous rage. Batman eventually showed up to save Robin; during the scuffle, the Dark Knight also relied on the shark repellent. As such, the singular gadget is somewhat of a running gag now.
While it may seem like the kind of knowingly camp elements that permeated the Batman series of the 1960s, the shark repellent actually has roots in the comics. In any case, its use on Harley Quinn conveys the show's attention to detail. It was also a testament to the show's effectiveness at walking the line between parody and reverence - both the comics and the myriad adaptations from across the decades. It is by far not the only reference and Easter egg in Harley Quinn. However, it's one that will assuredly delight the many fans hold the 1966 TV show and movie close to their hearts, and who still believe that West is one of the best versions of Batman to have ever graced the screen.