Batman: Arkham Asylum
- While attempting to secure Dr. Young's notes on the TITAN project, grappling up to the top floor near the chandelier before going down the stairs will result in The Joker cheekily admonishing you for "reading the last page first". He'll also berate the mooks for "not doing their job" and send them away if you grapple up before you fight them. Coincidentally, this avoids the risk of having someone being crushed by the chandelier when Batman makes it fall into the glass floor below.
- At the end of the game, the entrance to the final confrontation with Joker (which he's anticipating and has set up as a party) is blocked by some mooks who tell Bats to go back because he's not on the guest list. You can, of course, fight the thugs to get in; but if you just go back as soon as they tell you to, they'll be stunned that Batman has actually listened to them, and say this wasn't part of the plan. And then they proceed to attack Batman anyway.
- When you visit the Botanical Gardens, you can shut down the power in a certain hallway before entering it. If you do so, Joker compliments Batman for "always being one step ahead", and a cutscene that triggers in the aforementioned hallway changes. Normally, Joker drops a guard into a puddle of electrified water before leaving and detonating the entrance. This way, he only does the latter.
Batman: Arkham City
- Early on in the game, there's a Riddler trophy in a cage connected to two question marks. You're supposed to wait until you get a certain item later in the game to beat it, but it's actually possible to get it immediately by standing on the target, using a quick batarang to hit the first target, then quickly switching to the remote controlled batarang, throwing it, boosting it to get it past the bars, then braking it and waiting for the second question mark to light up. The Riddler will then complain at you for cheating.
- It's entirely possible, using a glitch involving standing on a ledge and continually throwing Freeze Grenades on end, to glitch yourself up high enough in the game world to glide over the barrier surrounding Arkham City. Using this method, you can actually fly around and explore the rest of Gotham City. Yes, that big skyline you see in the background throughout the game was actually constructed and was fully detailed by Rocksteady (although the buildings are all hollow inside). You can glide around and watch cars passing back and forth on the bridges, fly to Arkham Asylum (which is also present, although significantly scaled down) and fly up high and see that the game world goes much further than just Arkham City. Most players won't even glimpse most of it (and it will glitch your save file out if you haven't backed it up elsewhere), but the fact that they put all this work into something most players would never see up close is nothing short of incredible.
- If a TYGER goon stands on a balcony at the top of Wonder Tower, you can perform a ledge takedown and leave him dangling high above the city. However, you're not allowed to cut him down with a Batarang and send him plummeting to his death, because Batman doesn't kill.
- If you lose as Bruce Wayne against Penguin's goons at the beginning of the game, the game will only play the first of Cobblepot's many Game-Over Man cutscenes, as it's the only one to not refer to the player as Batman.
Batman: Arkham Knight
- In the GCPD lockup, one of the items on display is the Remote Electrical Charge. You're required to have Batman steal this about halfway through the game to progress, but there's nothing stopping you from taking it long before the campaign requires Batman do so. If you wait to do this until after the Joker becomes your Spirit Advisor, he'll have something to say about it. The police officers guarding the evidence lockup will also say some unique dialogue as Batman leaves, mostly wondering if Batman's allowed to do that, but none of them wanting to be the one to try and stop him.
- In what might be a Continuity Nod to a similar detail from Batman: Arkham City, if you check Barbara Gordon's body after her apparent suicide while in Detective Mode, you'll notice that her skull is remarkably intact for someone who's just blown her brains out, hinting that her death was just an illusion.*
- Furthermore, in an even more obscure example, returning to the above room before the Arkham Knight HQ level, you'll find that Barbara is no longer in the chair, replaced by Joker mockingly pretending to be dead. He comments on that the body is no longer there. Sticking around causes him to theorize that Gordon retrieved his daughter's corpse. The fact that the game brings attention to this is pretty impressive foreshadowing, especially since it's very unlikely most first time players would return to this room that has no purpose for the rest of the game.
- During the playable rampage as the Joker, you can find Penguin cowering away in a corner, begging for his life upon seeing you. Joker has a quip for whether he spares Cobblepot ("Okay, but only because you grovelled so nicely.") or if you kill him ("I never could stand grovelling, Cobblepot."). If you choose to spare Penguin, walk a fair bit away, and then turn back around and shoot him, Joker will say that he changed his mind.
- Early in the game, Batman is given intel on the Riddler from the GCPD. Later on, as you are working through the main quest, the Riddler will tell you that he's kidnapped Catwoman, and to complete a race track to obtain one of the keys to unlock the 10 locks to Catwoman's bomb collar. If you complete the race track before he kidnaps Catwoman, you don't get the key, and the Riddler doesn't tell you about his next challenge until after kidnapping Catwoman. After you complete the second challenge and use the key, he will tell you that he decided to make the challenge count for two locks.
- After completing the Riddler's "final exam", Catwoman can continue to duck between the now-perpetually spinning threshers instead of jump up to the ceiling, prompting Batman to comment on it:Batman: ...You can leave at any time.
Catwoman: (Defensive and embarrassed) I knew that! I just... like dodging the saw blade.
- In challenge maps, if you die in the vents when the enemies gas them, enemies will continue searching for you, since they don't know you died.