Warning: The following contains SPOILERS for Harley Quinn, season 2, episode 3, "Trapped."
Harley Quinn season 2, episode 3, "Trapped," featured a number of Easter eggs and references to DC Comics supervillains within Doctor Trap's lair. First appearing in Chase #6 in July 1998, Doctor Trap is one of DC Comics' most obscure supervillains.
The bad doctor was originally established a foil for DEO agent Cameron Chase and has barely appeared in a dozen issues since his introduction. Still, to give credit where credit is due, Doctor Trap was formidable enough an opponent to turn his own mind into a telepathic minefield that confounded the Martian Manhunter; no mean feat for an ordinary man with no powers or special talents beyond a penchant for outwitting super-powered people and deg deadly devices catering to their weaknesses.
In DC Universe's Harley Quinn, Doctor Trap set up shop in a New New Gotham museum."Trapped" sees Harley Quinn, Poison Ivy, Catwoman and Kite Man breaking into Doctor Trap's lair, in search of Firefly's flame-thrower, which Harley needs to break into Mr. Freeze's hideout. Finding it inside the museum Doctor Trap adopted as a base proves easier said than done, as Doctor Trap, predictably, filled the museum with booby traps to discourage anyone from disturbing him or trying to steal his collection of other supervillains gear.
Many wonderful toys are revealed as Harley, Ivy, and Kite Man make their way through the museum, offering a Who's Who guide to some of the world's greatest evil-doers. Here's the rundown of every DC villain artifact on display in Doctor Trap's lair.
Azrael's Armor
When Harley and Ivy first arrive at Doctor Trap's lair, a familiar looking set of armor can be seen immediately on the left in the main room. This appears to be the armor worn by Jean-Paul Valley in his Azrael persona. While nominally an anti-hero in most of his incarnations, the last scion of the Order of St. Dumas has fought Batman several times over the years, particularly in the reality of the Arkham City video games.
Black Mask, Nite-Owl & Other DC Masks
The next display case contains a number of notable villain masks. The first one on the left is instantly recognizable as the black wooden mask worn by Black Mask. Presumably the Birds of Prey villain is dead in the reality of Harley Quinn, as it seems unlikely he'd leave his trademark mask behind to be looted if he were still alive and kicking in New New Gotham.
The next trio of masks in the center of the case present a strigformian theme, being the masks of Owlman, Talon, and Nite-Owl. Watchmen universe, who had never visited any version of the DC Universe until recently.
At first glance the final mask on the far right end of the case seems to belong to Suicide Squad mainstay Deadshot. The mask sports the same distinctive red eyepiece favored by Floyd Lawton. However, on closer examination, this mask seems to be a clever forgery, as the eyepiece seems to have been placed over the right eye rather than the left.
Two-Face's Giant Coin
The next item in the main room of the museum is an over-sized, double-headed silver dollar with one face scratched up, suggesting that this giant coin belonged to Batman: The Animated Series episode "Almost Got 'Im," where Two-Face told the tale of how he almost killed Batman by flipping the giant coin while The Dark Knight was tied to it. Naturally he got loose and survived the incident.
The Bat-Cave's T-Rex Model
Speaking of trophies from the Bat Cave, the large model of a Tyrannosaurus Rex next to the giant coin resembles a similar dinosaur that is also often seen in the Bat Cave. The origin of this trophy has also changed over the years, but it was first connected to a case depicted in Batman #35 involving a prehistoric theme park where the dinosaurs ran amok. However, unlike Jurassic World, these dinosaurs were robots rather than the real thing.
Related: Harley Quinn: Riddler's Evil Scheme Is The Most Pointless College Ever
The Penguin's Trick Umbrella
Harley decided to seek outside help before venturing further into Doctor Trap's lair after encountering this case, which contained one of The Penguin's trick umbrellas. Harley figured the umbrella had more value as a collector's item now that The Penguin is dead. She also figured, correctly, that the case was trapped and that she needed the expert help of Catwoman to proceed safely.
Egghead's Egg, Doctor Fate's Helmet & Azrael's Sword
While he doesn't get much exposure in modern Batman comics, the super-genius crime-boss Batman: Arkham Knight.
Deathstroke's Sword
After Kite Man is caught in a net, Harley needed something sharp to cut him loose. Thankfully, Doctor Trap had the sword of Deathstroke the Terminator on-display close by. Slade Wilson's sword is another item that was often displayed in the trophy room of the Bat Cave. Given the giant coin and dinosaur in the main room it begs the question... did Doctor Trap loot the Bat Cave along with all the supervillain lairs in Gotham City?
Scarecrow's Mask
As Harley and Kite Man share a moment (or, at least, Kite Man tries to share a moment with Harley) a familiar looking burlap sack/noose combo can be seen on display in the background; the mask of Scarecrow. Dr. Jonathan Crane died a painful death in the Harley Quinn season 1 finale, burned by acid after annoying The Joker one too many times. How Doctor Trap got it from the ruins of Joker's collapsed tower base is anyone's guess.
Related: Harley Quinn Changes Batgirl's Origin Story
Charlie Brown's Shirt Pattern Vase
While not a supervillain artifact, it's still worth pointing out this vase, which can be briefly seen as Kite Man accidentally trips a spring-loaded step that sends him flying. The yellow vase seems to be imprinted with a black zigzag pattern, which makes it look distinctly like the shirt worn by Charlie Brown. As every Bat-fan knows, Kite Man's real name is Charles "Chuck" Brown.
Firefly's Flame Gun
The object of Harley's quest, Firefly's flame gun is perhaps the most deadly fire-based weapon on Earth. Personally designed and constructed by Gotham City's most infamous pyromaniac, this plasma flamethrower is just the thing for burning your enemies when heated words just won't do. Sadly, we have no idea if the Firefly in Harley Quinn's reality is Garfield Lyons or Bridgit Pike.