The bird skeleton Joker carries with him is a canary. Miners would bring canaries into mine shafts to monitor air quality. If the bird died, they would evacuate. Today, we have equipment to verify air content as well as oxygen levels.
Robin: Someone got a case of the giggles.
(Batgirl looks at Batman and Batman nods, signaling it's her)
Batgirl: (gasps) No. Well, I must have been really out of it. I hate pearls.
Joker: This is the cuckoo choo-choo, now leaving on track nine! Next stop: city limits, and the end of Gotham as we know it!
Batgirl: Well, got to go.
Batman: And where are you off to in such a hurry?
Robin: Late for a train?
Batgirl: Midnight madness sale at Gotham Shoes. You coming with me?
Robin: She's a regular joker.
Batgirl: I hate to say it, Batman, but he's right. There's no way we can catch Joker now.
Robin: We've got nothing.
Batman: Not so. (looks at dynamite attatched to rock) We've got explosives.
(After Batman blows a wall in the Batcave)
Alfred: Good heavens!
Batman: Sorry about the mess, Alfred.
Alfred: The front door too conventional for you, sir?
Batman: In the late 1800s, Gotham was a striving coal-mining town. Who knows how many tunnels riddled the city's foundations?
Joker: Ooh! Crime-fighter and history professor all in one!
Joker: What's the matter with the lights?!
Batman: Your scheme has just been de-railed.
Batgirl: You know, it's really a shame to seal it up. Maybe you should expand. Add a Batgirl cave!
Robin: Batgirl cave?!
Batgirl: I'm old enough to have my own cave. I can park my cycle there, bring in some exercise equipment, a couple of bean-bags …
Robin: How come she gets her own cave?
I want my own cave!
Batman: Nobody's getting their own cave.
Bruce: After her morning shopping trip, Barbara took the train to school.
Dick: Let's just hope they don't have a shoes store on campus.
Bruce: Joker did something to Barbara at some point during her day.
Dick: Yeah, and by retracing her steps, we're hoping to figure out when and where. But, Bruce! We just spent the last two hours watching her shop for handbags!
Bruce: Well, you're in luck. I think she's moved on to the main event.
Dick: Comic books?
This is the only episode that doesn't feature Harley Quinn with the Joker since her first appearance.
This marks Mitch Pileggi's ("Commissioner Gordon") final episode.
This is the first and only episode of the season to feature all five main characters (Batman, Robin, Batgirl, Alfred and Gordon).
This is Commissioner Gordon's first appearance since the second part of "The Joining".
Robin vs. Batgirl
When Robin pins Batgirl (under Joker's influence) to the wall, she runs up the wall to get free. Robin used the same trick on Terra in the Teen Titans episode "Aftershock (1)". Apparently, this is where Robin learned that trick from.