A couple of old ladies tell a pair of trick-or-treating children the tale of Solomon Grundy, a swamp zombie who is supposed to come back during Halloween lunar eclipses to wreak vengeance on the descendants of Gotham's founders — them included. Much to their horror, Grundy arrives and wrecks their house, putting Batman on his trail. Has Grundy really come back, or is a supervillain taking advantage of the old legend?
This episode contains examples of the following tropes:
- Bait-and-Switch Boss: The episode builds up Solomon Grundy as the villain, only for it to turn out to actually be Clayface using his identity.
- Batman Gambit: Clayface explains how posing as Grundy is the perfect cover. Even if people genuinely believed the zombie is real, the first place they'd go looking for the stolen goods is the swamp and try dredging it, which would give him plenty of time to head off with the spoils.
- Book Ends: The episode began with the two boys who were told the story of Grundy by Fulton's granddaughters. At the end of the episode, the same boys appear again in Gotham Swamp, waiting for Grundy to rise up, then flee when he does.
- Corrupt Corporate Executive: Fulton, Winslow, and Parish, who decided to pollute Gotham Lake with industrial waste, turning it into a swamp and robbing the inhabitants of everything they had.
- Dramatic Drop: The two old ladies drop their teacups when Grundy arrives.
- Evil Is Cool: An In-Universe example. Three Trick-or-Treaters were dressed as Joker, Penguin, and Catwoman. Bruce surmises this is the reason for the costume choices.
- Evil Is Hammy: After his ruse is exposed, Clayface stops acting like a stoic, angry zombie and indulges in being hammy.
- Evil Sounds Deep: Clayface's Solomon Grundy disguise was voiced by Kevin Grevioux of Underworld fame, so naturally Grundy has basso profundo going on.
- Faux Affably Evil: Clayface engages in "friendly" dialogue, while trying to beat Batman to death.
- Flashback: When Alfred explains the Grundy legend. Laborers used to live at what had been Gotham Lake, but Fulton, Winslow, and Parish turned it into a dumping ground for their construction of the city, rendering the spot an uninhabitable swamp. Some of the laborers were versed in magic and created Solomon Grundy from the waste on All Hallows' Eve during a lunar eclipse.
- For Halloween, I Am Going as Myself: Of a sort—the episode takes place on Halloween and while he's out looking for "Grundy," Bruce (in his Batman-attire) is, at one point, mistaken for a partygoer in a Batman-costume by a civilian. Bruce decides to roll with it and claims that he's looking for a friend of his who's dressed up as Solomon Grundy for the holiday.
- Halloween Episode: The Grundy curse is purported to have been cast on All Hallows' Eve during a lunar eclipse. As such, while kids are out trick or treating, Clayface poses as Solomon Grundy and trashes mansions in order to steal fortunes. Clayface also exploits passersby being in costume in order to make discreet exits.
- Hidden in Plain Sight / Nobody Here but Us Statues: When Batman exposes him in his Grundy form, Clayface runs into the wax museum.Batman: A shapeshifter in a wax museum. Great.
- Hoist by Their Own Petard:
- The laborers created Solomon Grundy from the very waste that Fulton, Winslow, and Parish had dumped in the lake.
- Clayface attempts to dispose of Batman by dumping him in a vat of hot wax. As Batman escapes this, he throws a batarang at the chains holding up the tank pouring the wax. Clayface gets caught in the resulting spill and is immobilized.
- Ironic Nursery Rhyme: Gotham apparently has a poem about Solomon Grundy: "Grundy will come on dark Halloween night/To deprive the descendants of all in their sight."
- Jerkass Ball: This is the only episode in which Ethan Bennett is truly villainous in the Clayface role, with the only episode featuring him after this having him return to his previous Anti-Villain characterization.
- Laser-Guided Karma: According to the legend, in response to Fulton, Winslow, and Parish turning Gotham Lake into an unlivable swamp, the laborers who lost their homes used their native magic to form Grundy from the swamp, sending him after the three architects and their descendants throughout the ages, leaving them destitute. Alfred considers it poetic justice at it's most spine-tingling.
- Our Zombies Are Different: As usual, Solomon Grundy is depicted as a swamp zombie.
- Pay Evil unto Evil: Fulton, Winslow, and Parish caused the laborers to lose everything, so the laborers ensured they would suffer the same fate.
- Properly Paranoid:
- Batman is immediately doubtful he's dealing with a supernatural creature, even after the first fight, and runs a DNA test on some recovered mud. When Alfred later reports there is mutated human DNA there but not on any follicles or skin, Batman immediately guesses the DNA is in the supposed mud itself.
- In the end, Bruce thinks this all proves the legend was never real, but Alfred says that a villain pretending to be Grundy doesn't mean the real Grundy isn't out there. The final scene proves him right.
- Real After All: In the penultimate scene, Alfred points out that Clayface's hoax doesn't prove that Grundy isn't real. This leads to a final scene with the two children from the opening sitting by the swamp. Just as they pass the story off as false and turn to leave, the swamp begins to bubble and they hear moaning, causing them to start running. In the comic spin off he makes several appearances with his first having Batman believe he was Clayface again.
- The Reveal: In his second confrontation with "Grundy", Batman tells him to lose the mask and slaps him in the face, with traces of mud left on his hand.Batman: Trick or Treat...Clayface.
- "Scooby-Doo" Hoax: "Grundy" isn't Grundy. He's Clayface, taking advantage of the legend to rob the descendants.
- Sins of Our Fathers: The curse applies to all descendants of Fulton, Winslow, and Parish.
- Super-Strength: Grundy/Clayface. He can reduce a house to rubble in minutes.
- That Man Is Dead: Batman considers that Ethan Bennett is truly gone, as shown during his confrontation with Clayface, with him continuously referring to him as such.
- Villain Ball: Grundy/Clayface had the chance to kill Batman outright after the first fight, but he simply left him for dead in a collapsing building.
- Wham Line: "Trick or treat, Clayface."
- Wham Shot: Battling the supposed Grundy, Batman goes for the face. What he rips off is shown to be a mud-like substance, revealing the true perpetrator.
- Your Costume Needs Work: Inverted—as noted above, Bruce (while in his Batman-attire) is mistaken for a regular person in a Batman-costume by a civilian, who compliments his costume. Batman decides to play along with this and asks the civilian if he's seen a "friend" of his who's dressed up in a Solomon Grundy-costume.
