After accidentally destroying one of Babs' beloved, one-of-a-kind Batman keepsakes, Diana enlists the help of Harleen Quinzel in order to find a replacement in Gotham City.
- Attention Deficit... Ooh, Shiny!: When Diana insists that Harleen stop taking detours, Harleen states that from now on she'll be laser focused on their mission. Then she starts chasing after a butterfly.
- Bait-and-Switch: Harleen stops by Crime Alley, and begins telling a tearful story about how "two beautiful gems were lost one day." For those familiar with Batman lore, she appears to be setting up the story of how Bruce Wayne's parents were killed; instead, Harleen was referring to two jawbreakers she lost. She even discards a couple of stray pearls found in the alley.
- The Cameo: Mr. Freeze, Catwoman, and Penguin are shown during a description of past Gotham crimes. And one person in the crowd that mobs Diana might be the Scarecrow, as he's accompanied by a flock of crows.
- I Can Explain: Harleen graffitis a wall in order to grab Batman's attention. Diana starts trying to clean it off when, lo and behold, Batman appears. Thankfully, he's a Reasonable Authority Figure and believes Diana's excuse. The fact that Harley Quinn tried to attack him also distracted him from the issue.
- Internal Reveal: Diana alone finally figures out that Harleen Quinzel is really Harley Quinn.
- Meta Origin: According to Harleen, the Joker, Mr. Freeze and Clayface all got their origins falling into vats of chemicals at different Ace Chemical facilities.
- Mythology Gag: Sprang Station is named from Golden Age Batman comics artist Dick Sprang.
- Shear Menace: Harley intends to cut off Batman's cowl ear with a set of giant safety scissors.
- Similar Item Confusion: The plot gets started when Diana mistakes the keepsake, an ear from Batman's costume, for a whetting stone, ruining it by sharpening her sword with it.
- Underestimating Badassery: Like every other version of Quinzel, she's a lot more clever than others give her credit for.
- Welcome to the Big City: As soon as Diana steps off the bus into Gotham City, she is mobbed by a crowd and has her backpack stolen.
- Wham Episode: The episode ends with Diana fully learning that Harleen Quinzel is Harley Quinn, but forced to keep quiet about it when Harleen calls her on the "favor" from earlier in the episode.
- You Owe Me: For helping her get another Batman ear, Diana vows to repay Harleen someday. When Diana realizes Harleen is really Harley, she's about to reveal it when Harleen invokes the favor to keep her quiet.
