Bruce is obviously shocked by this stunt double that looks almost exactly like him. After a thorough investigation and a modified test that accounts for the strange substance bonded to his DNA, Bruce finds out that they have no family relation, and they really do just happen to look like each other.
Danny is doing his best to get out of the limelight. He had his moment of fame as a teen, and that was more than enough for one lifetime. If he never has to see another shrine to himself again, it will be too soon. The thought of it makes him shiver. Of course the movie's producer sees this as free publicity and only fuels the media fire.
When some raw footage of one of his film sessions 'leaks,' a massive media flurry of "do the butts match?" whips the media storm into a full-blown tornado. Because Batman is the only one who could pull off stunts like that in real life. Danny's further denials just make everything worse, until Batman himself shows up next to Danny to prove his innocence before it can get too far. (Much to the producer's consternation)
Everything quiets down after that, much to Danny's relief. It's not perfect, and the rumors of a long lost twins still circulate, but it's bearable. Even the proof of Danny's parentage isn't enough to dissuade the more zealous fans. He just needs to finish filming and get the hell out of dodge.
Filming is almost over when disaster strikes.
A villain (maybe the Riddler), somehow catches a glimpse of Batman without his mask and knows its Bruce freaking WAYNE under there.
Knowing that facing Batman head on to unmask him was a doomed endeavor, they target Bruce Wayyne instead. They publicly kidnap him with a live broadcast to all of Gotham. Multiple cameras showing every angle of Bruce tied to a chair while the villain rambles. Bruce can't so much as twitch in a competent manner, or his Brucie persona will be done for. No morse code blinking. No falling in a convenient manner. Nothing. The villains claims that he is Batman aren't confirmed, the idea is already planted. There's no way out of this.
So it's up to the Batfam to arrange the rescue, and they knew exactly what to do!
The solution is obvious. They need Batman to rescue Bruce on live television such that nobody could suspect a fake Batman or impersonator. This would clear Bruce's name completely and blackmailed material for the future. This wouldn't be the first time they've needed to pull the ol' switcharoo.
Naturally, Batman swoops in like an avenging tide of darkness. Beats up the villain and their goons in true Batman fashion, with an amazing fight full of flips and punches and leg sweeps all while bouncing off walls and wrapping goons up in cables and whatever else is around. There is no doubt. This is the real Batman. Only someone who has been fighting for justice their entire lives can move like that, all while expertly protecting the hostage.
All too quickly in the views opinions, the villain is tied to the very chair they trapped Bruce to. But the show wasn't over. Bruce was on the floor, legs shaking too much to stand. Without a word, Batman effortlessly lifts Bruce bridal style and carries him to safety. Never one to miss an opportunity, Brucie Wayne immediately starts batting his eyelashes and flirting enough to make grandma blush. Batman's stoic expression doesn't even twitch as they exit frame and out of sight.
As soon as they make it to a safely secluded spot away from prying eyes and ears, 'Batman' sets Bruce down then promptly doubles over laughing.
Used to it, Bruce rolls his eyes and sighs. "I'm surprised you showed up, Dick."
Instead of answering the unasked question of 'how did you get back so fast when you were supposed to be off planet,' 'Batman' is far too busy suffocating and collapses to the ground.
He finally answers when the giggle subsided enough to breathe again. "H-How-How-How do you keep a straight face like that?! I almost pissed myself when you started squeezing my bicep and calling me 'hunkaliscious'!"
Bruce freezes. That wasn't Dick's voice.
Danny bounces to his feet, pulls the cowl back, gives a dramatic bow with a wink. "Your one and only stunt double, at your service."
Danny lifts his hands in innocence. "Not my fault! I was trying to avoid getting involved with your nightlife. Been there done that. But when a bunch of teenagers try to kidnap you? I make an exception. Plus, I have to admit, this suit makes me feel like a badass. How are you not grinning like an idiot all the time strutting around with a cape?" Danny pulls it up to his face like a cheesy vampire. "I am the night."
"How did you figure it out?" Bruce pulled out all his Batman intimidation. This was bad. This was bad. This was really, really bad. A civilian knew his identity.
Danny just gave him an unimpressed look, not the least bit intimidated. Honestly, it felt more like getting threatened by a puffed up kitten. "Normal people don't reak of death. I've had you clocked since the "do the butts match?" Incident. Thanks for the save, by the way. The last thing I need are stalkers. Those guys are ruthless. You can keep 'em'."
Danny sobers when he senses Bruce's anxiety. "Don't worry. I know how important secret identities are. I promise no one will learn about it from me."
Something in his voice and eyes makes Bruce relax. He believe it.
That's when a rainbow horde of teenagers vault down into the alley, practically jumping on Danny who laughs along with their antics. They rambled about how perfect he was and where did he learn that one wall run then flip combo, completely forgetting Bruce.
He'd have to fix that. He cleared his throat. "Does anybody want to explain whose idea it was to force a civilian to impersonate me?" The response was instant. Everyone fell silent then scattered.
Danny looked at Bruce with a grin. "Can I watch you lecture them? I reeeeeeally want to watch you lecture them."
Bruce couldn't help a slight smile of his own. Maybe letting this civilian hang around for a bit wouldn't be such a bad idea. It was always good to have a back up plans anyway, and Dick couldn't always be around when he needed a double. This was just for contingencies. Nothing else.
"Maybe I could arrange something."