Batman uses a capeless fireproof Batsuit in the final confrontation with Firefly. This Batsuit looks similar to the Batman costume in the Batman Beyond series. (edit) Batman uses Mr. Freeze's freeze gun to fight Firefly. That gun pops up a few times in later Batman animated series too. (edit) Robin, Nightwing, and Gordon are absent in this episode. (edit)

Bruce: So what are you doing tonight?
Barbara: The same thing we do every night, Pinky.
Bruce: What?
Barbara: Never mind. (edit) Bullock: Get some pictures. I'm gonna check the fridge.
Cop: Yeah, there's a lot of evidence in there, Detective.
Bullock: Shut up. (edit) Bruce: Who is this Cassidy, anyway?
Shannon: Only the hottest singer in the world, Bruce. What cave have you been hiding in? (edit) Cassidy: Let it go, Garfield. Whatever you thought we had is as cold as a burnt-out fuse!
Garfield Lynns: Hey! You're the expert on burning people, you little tramp! (edit)

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Barbara: (answering Bruce Wayne's question "What are you doing tonight?") The same thing we do every night, Pinky.
This exchange is a variation of the lines that begin and end every episode of Pinky and the Brain, an animated series about two lab mice who spend each night trying to take over the world. At the time this episode first aired, both of these series aired on the WB, so this was probably an in-joke. Naturally, Bruce had absolutely no idea what Barbara was talking about. (edit)