Moments later, newspaper photographer and screeching damsel Vicki Vale tries to distract the Joker by kissing him. She macks his big purple jacket in a way that's not erotic or distracting, but makes everyone in the cast feel terrible for her.
"Lint gets me so hot."
Vicki Vale has been kidnapped by Batman or the Joker at least four times in this movie already, depending on how you count. When you spend your life being dragged around by costumed psychopaths, awkwardly smooching someone's jacket is as close to a master plan as you're going to get. And then she drops down, and the Joker thinks, "Five minutes ago she hated me. This is going so much better than I expected."
Spoiler: His balls are about to match that tie color.
Surprise! It's the old "Think you're going to get a blowjob from a lady who loathes you but she's actually setting you up to take a punch from Batman" gag! Oldest trick in the book! How is it possible for the Joker to get so distracted that he doesn't notice a fully-armored, wounded Batman limping up next to him? I don't want to pretend that I've had sex multiple times before and am some kind of romantic master, but I feel like I'd know if Batman was within arm's length of me, even if I was getting to second-and-a-half base with Kim Basinger. And Jack Nicholson had already been having sex with the only other lady in Gotham, so it's not like he was so sex-starved that a little clumsy attention from a woman was going to upend his plans.
And before you argue that Batman is known for his stealth, let me counter with every other Batman-related scene in the movie, in which he fought evil by walking up next to it and watching it fall down. If Batman suddenly decided that maybe he needed to try out this whole "stealth" thing that the League of Shadows would always go on about, he certainly picked a weird opportunity to do so.