Batman: Arkham Asylum/WMG

Batman keeps down crime in Gotham City partly through brutal (but efficient) birth control
Well, many of the thugs he meets in this game probably won't be having kids in future after his bone-shattering crotch kicks, and children raised by criminals are statistically much more likely to become criminals themselves.

Titan isn't JUST an altered Venom: It's mixed with the Blacklight Virus.
As an extra power booster, they were mixed, which is why their spines can stick out with no damage to them because of it.

You spend the entire game taking on hordes of mooks, battling all manner of nasty bosses, and experiencing many Crowning Moments Of Awesome, all for to go down with almost no sense of a real fight at all. Disappointed? He was counting on it.
 * Makes sense actually... he could be setting up for something even bigger ie a sequel. Just as the unmentioned adventure before the game started was, as Batman said himself, "too easy", Joker may have at some point decided that this current plan was failing in a way he didn't like and simply started up a new plan using this one was a stepping stone. Or otherwise felt the jokes weren't amusing anymore and wanted to pull a new gag. He is Crazy Prepared much like Batman, after all. Unlike the unmentioned adventure, by using this one which is certainly not 'too easy', Joker could start into motion other things without Batman initially suspecting. And heck, if it was what the WMG suggests from the start, seeing his mooks get pummeled across Arkham is probably good for laughs.
 * ... Yeah.

Two-Face is going to be in the sequel
On the Arkham Has Moved website, there's a play on the Uncle Sam "I want You" poster. The face has been torn off, however, the character's clothing is two tone, divided along sides of his body.
 * As above, makes sense since the game ends with Batman chasing Two-Face.

Warden Sharpe became mayor between the two games
Riddle me this, tropers: why would any sane person relocate Arkham to the middle of Gotham? Trick question; only an insane person would do it. The Spirit of Arkham messages make it clear that Sharpe is a total lunatic who sees humanity as inherently evil and rotten, and early in the game we hear that he's interested in running for mayor. So imagine the scenario: Sharpe is elected and moves Arkham, ostensibly to better deal with inmates and prevent incidents like those from the first game, but in his own twisted mind he just turned Gotham itself into one big asylum for the diseased vermin of the city, preventing them from getting out and "infecting" the wider world. And the only person who knows Sharpe's a loon is Batman, and nobody aside from Jim Gordon's going to believe him.
 * Hm... alternatively, he doesn't strictly move Arkham so much as simply declare Gotham at large a part of Arkham. Either way, I could see Sharpe being a major villain in the second game and having characters like Lockup, Anarky, and similar extremists on his side.
 * I can't see Anarky working for Sharpe -- Sharpe seemed pretty authoritarian, and Anarky is pretty much all about anti-authoratarianism.

There will be a voting poll as to who got the Venom at the end of the first game, and whether or not they have an important role in the sequel.
I mean, come on, how else are they going to choose who got the Venom?
 * By saying all three got it.
 * Which one got it depends on your difficulty level in this game. Why not in the sequel? Failing that, the true ending was what you got on hard.
 * No, it appears to be random: this troper got Bane for both Easy and Normal finishes.
 * Actually, it's the boss you died most on. If you didn't die on any of them, or it was a tie, then it probably is random.
 * It's random - I died most often on Scarecrow (my controller sometimes doesn't recognize when I want to stop moving), followed by Bane, and ended up getting Croc.

Quincy Sharp is a Quincy.
Hey, it's Wild Mass Guessing, remember? He is also one of, if not the best quincy, and therefore a sharp quincy. This later became his codename, after he reversed it.
 * Alternately he's A different Quincy, still a megalomaniac. Or maybe Yet another Quincy?

Mayor Sharp is actually possessed.

 * While the first game never out right said it, me thinks that ol' Sharpie was, and still is, possessed by the ghost of Amadeus Arkham. It's obvious that the first half of the tablets were from Arkham, with the later ones eventually being from the Warden. Much like Deadman, only evil absurdly zealous, Arkham is using Sharp to carry out his desire of cleansing Gotham of its evil. This would also explain why in the Spirit tablets, Sharp is cold and sadistic sounding, but during the game comes off as a coward who fears for his life (of course, he could just be playing the part). This would also explain how he dissappeared from the island and why the runic symbols were on the floor.

The whole night could have been avoided by Batman pulling a Screw This I'm Outta Here
And that's the other thing. The Joker controls Arkham, all the inmates are freed, and some of them are superpowered psychopaths. Even in the extremely unlikely event that the Joker does just "give up", do you really think everyone else is just going to go, "Oh, sorry to be a bother, I'll just go back into my cell now." And don't forget about all the innocent people on the island. Guards, doctors, police officers, legitimately sick people who aren't supervillains? They'll all be perfectly fine on the isolated island filled with murderers, thugs, and superpowered freaks, I'm sure.
 * Yes, because leaving the Joker with Arkham under his complete control, along with all the villains running loose, hundreds of mooks to brainwash and enhance with Titan, is just a wonderful idea.
 * Not the way I see it, for one of two reasons: 1) Joker wanted Batman to go Crazy, so if Batman would not play along, Joker would give up. 2) Joker would be so confused he ends up standing out in the open and getting clobbered... or somthing like that.
 * ...Wow, no. Either one is completely and totally out of character for the Joker.
 * Batman never gives up, so we don't know how Joker would react to it... (I think) For all we know he would take it designing to go into opera singing. Besides, he is nuts.
 * "He is nuts" doesn't mean he's entirely without any sort of rhyme or reason. He's obsessed with Batman. If Batman just left, he'd take it most likely as a personal insult. Given that he has complete control over everything in Arkham, he could still very easily complete the formula, and go after Batman instead. The Joker doesn't just "give up" if one bit of his plan doesn't go exactly as he thought it would.
 * Well at the vary least, Joker is off his A game after that. He is obsessed with Batman, so he's not only insulted, he is hurt. Makes a mistake and the heads off the Beast. Who out? Zazzs? The guards could have handled him. Harley and Scarecrow were not expecting to defend themselves from where they were. Mooks are stupid.
 * You mean the mooks that killed most of the guards and took over the place in the opening? And the guard that Zsasz took hostage and nearly killed right at the start? Yeah, those guards did a stellar job of handling those "stupid" mooks. The Joker didn't take over the place single-handedly, you know. Joker being off his "A game", if that's even what would happen, isn't an Instant Win Condition.
 * The Joker wants to drive Batman crazy. If Batman abandons a bunch of innocent people on an island full of supervillains (even if those people ultimately somehow prevail against Ivy, Scarecrow, Croc, and Clayface), Joker has won. That leaves him with a small army and a nice Psycho Serum to play with as he figures out his next goal...
 * And even if it would somehow defeat Joker if Batman just up and left (which, as noted above, is unlikely), let's face it -- Batman's not just going to leave and let the Joker run around and do whatever the hell he wants on Arkham Island, even if he does give up eventually. That would probably mean innocent people would end up dying and suffering, and as long as he's around he can protect them.

The giant plant Poison Ivy summons during her boss fight is actually the true Ivy

 * Think about it: everyone else who has been exposed to the Titan mutates into a huge monster, but when you first see Ivy after she gets a dose, she hasn't changed a bit. That's because "Poison Ivy" is actually a plant duplicate, while Ivy herself has mutated into a giant flower.
 * Or because Beauty Is Never Tarnished.

The spirit of Amadeus Arkham is Slender Man.
Warden Sharp became a Slender-agent, much like totheark (Ark as in Arkham?).
 * Or perhaps ol' Slendy is just manipulating Sharp into thinking he's Amadeus. After all, let's not give Slender Man a definitive origin... although now that I think of it, a Batman and Slender Man crossover would be amazing. Can we get Doctor Who into this too?

Batman actually kills on occasion, just not on purpose
Do you think all of the goons he fought survived? Given the pounding he gave them, many would have succumb to internal bleeding and head trauma. Both Batman and Gordon see these as 'acceptable losses'.
 * I believe it, I mean, do you honestly think being pulled off of catwalks to the ground, being strung up on gargoyles and being cut down head first (and you can hear cracks when Bats pulls off some attacks), and the explosive gel sending the shrapnel at the goons, etc. would not end up with death or at least someone being paralyzed?! Because if you do, you're nuttier than the Joker and Deadpool combined.

Batman unintentionally kills henchmen during the Scarecrow hallucinations.
There's some pretty brutal damage done to the skeletons in those levels, and in the sequel when  is framing Bruce Wayne for a string of murders, Barbara tells Bruce she's afraid it might be true, saying something along the lines of, "What if Crane got to you again?" (Emphasis mine.)

The REAL reason Ivy doesn't transform
Titan is administered via injection. For an injection to work, it has to get into the bloodstream. So why would it work normally on someone with chlorophyll in her veins?
 * So the titan plants have a bloodstream then?