Alas, Poor Villain: In-universe. Aya may have some somber reflections on some of the boss monsters after she's defeated them, including the garbage monster and the living power generator.
Apocalyptic Log: A few are found, in particular one left by a researcher over a couple of days describing the evil Dr. Bowman who eventually turned into an ANMC. The second-to-last entry is of her writing about how she let him out of his cage because he wouldn't stop complaining, and noting that he's now over nine feet tall. The final entry is by someone else, noting how the researcher was (unsurprisingly) eaten by Bowman.
You also run into a giant-sized version of a Brain Stinger.
Awesome, but Impractical: The Golems. All the research and effort that goes into their biological modifications and flashy laser weaponry is shown to be ultimately pointless as they are utterly wrecked by good ol' fashion infantry with good ol' fashioned guns.
Several weapons and attachments for the M4A1 are a lot more trouble than they are worth. A good example would be the M203 attachment. Grenades are powerful, but they are also rare, so you are more inclined to save them for bosses. The attachment also takes up a slot that could be occupied by something more useful, such as the Hammer.
Awesome Yet Practical: The Wind line of Parasite Energies. They have lower damage output than the Fire line, but they can inflict some very useful negative ailments. Apobiosis is arguably the most devastating, as it can damage everything and any surviving enemies are left paralyzed for a long duration. Very few enemies are immune to the paralysis and the icing on the cake is the stun effect works on the final boss' 2nd form.
The Hammer attachment for the M4A1. Its a huge cattle prod that shoots bolts of lightning at enemies. The larger ones get knocked down or stunned, leading them open to critical hits. Smaller enemies are killed outright and it can destroy swarms of them like a shotgun. Best of all, it runs on battery power and is free to recharge at merchants and BP stations.
Barbie Doll Anatomy: Close-up analysis of the "Stranger" NMCs indicates that nipples may just be considered a disadvantageous evolutionary feature. This may, of course, be due to the fact that the "Suckler" NMCs detonate their own craniums as a self-defense mechanism, making breastfeeding quite the chore.
Boring, but Practical: Of all the cool weaponry you can get in the game, they're either too expensive/unavailable until later in the game or Awesome, but Impractical. Pistols are probably the best weapon to keep with you throughout the game. It's due to the fact that the game's critical hit are absurdly high with single shot weapons (including the paltry P08) and you get infinite basic pistol ammo in the form of random ammo boxes. Many strategies recommend you use nothing but pistols in the harder modes solely because of this fact.
Button Mashing: Used to wiggle out of an enemy's grip or to shake off the effect of paralysis.
Cast from Hit Points: The Berserker status increases Aya's weapon power and levels up her parasite powers, but at the cost of chipping away at her HP.
The Cavalry: The US military eventually intervenes, somewhat more competently than in the first game this time.
Door To Before: A few of them, including a very big one leading back to Dryfield from the underground shelter's sewer tunnel. In fact, it's so close that it's a wonder that you had to drive to the shelter in the first place; it's basically right underneath Dryfield.
Down in the Dumps: Aya needs to escape a sterilization room in the shelter by leaping into a dust chute into the underground dump. Almost immediately afterwards she's attacked by a giant vacuum-suction-mouthed garbage monster that formed in the trash heap and wants to add her to its stomach.
Just Eat Him: Said garbage monster's vacuum mouth attack is an instant game over if Aya gets too close.
Advancing Boss of Doom: The creature keeps slowly and implacably moving closer and closer, leaving you with less and less room to run away from it.
This trope also comes into effect when you have to escape the secret underground lab with Eve. While no enemies are present, Eve will start to cough from the gas filling the room and lose HP.
Extremely Short Timespan: After fighting through the Acropolis, Aya's adventures in Dryfield and the underground shelter last about 24 hours, going by the day/night cycle.
Fight Woosh: A quick inversion of colors, accompanied by a heartbeat sound effect.
Flavor Text: A striking amount of it, and you usually have to examine a background object several times to see it all. Many of Aya's inner thoughts are discovered this way, as well as background information on herself and others.
Follow the Leader: After doing its own thing in the first Parasite Eve game, Squaresoft decided to ape Resident Evil for this one, resulting in Aya investigating a seemingly abandoned area where an outbreak of man made monsters is occurring, eventually leading her to a secret underground base run by a powerful group with a lot of money and No OSHA Compliance. Also, Solve the Soup Cans puzzles and tank controls.
Gameplay and Story Segregation: Averted in the lengthy cut scene that takes place before the Final Battle. Aya winds up being shot in the leg and when you regain control of her, her remaining HP has been lowered to reflect her gunshot wound.
Glass Cannon: Aya is defintely weaker in defense compared to the first game due to the new armor and HP mechanics (it will be rare that Aya's HP ever hits 300) and she can die in just a few hits if you aren't careful. However, Aya has access to a lot of powerful guns if you know where to look and unlocking the 3rd abilities in each of Aya's parasite powers will make her even stronger.
Global Currency: Bounty Points (BP) are used primarily by the FBI's MIST unit, which gives them more goodies according to the number of monsters they kill (tracked by special contact lenses). However, they're also applicable to Dryfield's landlord Gary Douglas (justified, as the FBI said they would reimburse him for allowing Aya to use BP to buy stuff from his Wall of Weapons), the Neo-Ark Armory (A Chekhov's Gun lampshaded by Aya when her contact lens registers on the machine - Her boss is part of the conspiracy!), and soldiers operating out of the back of Army supply trucks (handwavable for the same reason as Douglas, since they're with the military).
Guide Dang It: About one-fifth of the gameplay. Of course, after a few repeat playthroughs, you'll be too strong to care.
A particularly nasty one is the four-part riddle you find scrawled in spots in Dryfield. One is written in glowing ink and can only be viewed if you don't turn on the lights in a dark cellar. One is written in a corner in a dusty antechamber before a boss fight, and immediately after that boss fight, it's night out and you can't read that riddle fragment ever again.
Many of the unlockable items require a very high score whenever you complete the game, but what the game doesn't tell you that A) NOT using the items you find and hoarding them instead gives points, B) playing on a harder mode like Bounty Mode gives you a bonus multiplier to your overall score and C) triggering certain events in the game gives you bonus points too.
The only way to return to Dryfield is blocked by a gate that requires knowledge of Japanese calender phraseology to open.
During the Acropolis section, there's a door in the chapel that is quite easy to miss. If you do miss it, you miss the series of events that allow you to get a keycard that will open an armory door in the Shelter. You don't need it, but it makes the Shelter levels a lot easier.
Hailfire Peaks: There are a number of different artificial environments right next to each other, including a jungle and a desert.
Harder Than Hard: Nightmare Mode, which combines Bounty Mode (stronger enemies in place of standard enemy spawns) and Scavenge Mode (items are harder to find/obtain, as well as being expensive to buy). The mode also reduces Aya's attack power and her base HP starts at 50 instead of 100. Beating the game on Nightmare gives you a 10x point multiplier for your next New Game+.
Hyperspace Arsenal: Zig-zagged: In battle, Aya does not have access to her entire inventory, just what she has equipped to her belt pouches on her body armor, which is fair. However, one item still takes up the same amount of slots whether it's a can of coca-cola, a bunch of bullets, or a grenade launcher.
Inventory Management Puzzle: Twenty items max, limited external storage besides, and you can only use stuff that you've loaded onto your current armor beforehand in battle. At least key items no longer counting towards this total helps buffer needing to carry around multiple ammo types.
Inner Monologue: Examining objects multiple times often reveals quite a lot of Aya's inner thoughts, some of which are actually pretty insightful.
It Can Think: The "stringer" ANMC we first meet is the mutated Dr. Bowman, and it talks. We never really find out how sentient the other ANMCs are or aren't; a bit of lore states that their individual minds are being suppressed by an implant that was supposed to be removed but never actually was.
Kill Sat: The "SDI Project - Hypervelocity Gun", as shown in the opening credits.
Lost Forever: Some items can't be found if you progress too far, mostly the Acropolis stuff, since it's the one place you can never backtrack to. There's also a weird case of a clue being lost forever. Four mysterious riddles are written throughout Dryfield, each giving you a number and telling you where the next clue is (the prize is the safe combination with a rare item in it). One of these four riddles, though, is in a very easy-to-miss spot (a window looking out on the desert) which is right before a local boss fight, after which it becomes night and you can't see the riddle anymore. Dang it!
Magikarp Power: The P08 is the lowest priced gun of all the weapons, but it's weak, slow, and has a small clip. Yet if you keep it in your inventory to the point when Aya can explore Dryfield's underground, checking the gun rack in the game room a few times will net Aya the "Snail Magazine". When used on the P08 its strength and clip increases and has an absurdly high critical hit rate.
Monogender Monsters: For some reason, all the Strangers we see are female, either in human form or out of it.
More Dakka: The 100-bullet full-auto pistol (among less readily available conventional machine guns)...
Multiple Endings: The game has three of them, depending on a few actions that you took. The standard ending has the President talking to his aide about what to do with the mess at the facility (this is all done in pure text behind a black screen). The better ending expands upon the previous scene and adds more details to the plot without a black screen. The best ending shows even more details of the plot and shows that Aya adopted Eve as her sister. A year later, they go to a museum where they encounter a man who is presumed to be Kyle.
Mysterious Waif: The Eve, Aya's clone, who doesn't talk until near the end. Aya ends up adopting her as a sister afterward.
Mythology Gag: The targets that Aya is shooting at in the intro are illustrations of the monsters of the first game.
No Body Left Behind: The monsters all melt when they die, but the cyborg Golems do not. Not even if you change rooms and come back later, which is especially surprising for a Playstation game.
Noob Cave: The shooting range in the MIST HQ, although you can skip it entirely if you wish. Tackling all the challenges and scoring high will net you some nifty items. The highest leveled challenge will cause damage to Aya but the challenge is automatically stopped if her HP gets too low with Pierce commenting "Now if this were real, you'd be dead."
Not So Different: No. 9 invokes this trope the first two times he and Aya run into each other, largely as a means of taunting her.
No.9: I'm a Hunter, jus' like you.
Nuke 'em: The government resorts to this in both games. Even though the soldiers in the second were actually quite successful in containing the threat, the President still decides (albeit hesitantly) to go ahead with it, while his troops are still on site.
General: "They'll be buried in Arlington. Proud heroes of the country."
Product Placement: Aya can drink cans of Coca-Cola to recover her HP and MP. A magnet (in the shape of a Coke bottle cap) is needed for a puzzle. Prominent Coke vending machines are placed throughout the game as well. Strikingly, these have been kept for the PSN rerelease.
Rare Candy: Protein Capsules, which recovers all HP and boosts max HP by 5. Lipstick increases maximum MP by 1.
Scenery Porn: For the time in which it was made, Parasite Eve 2's backgrounds are amazingly detailed. They were all pre-rendered and still-shots were used as the backgrounds, similar to how most Resident Evil games worked, but with much more work put into them. These places look like places where people worked, ate and lived; a lot of thought went into them and thus it brings a lot of verisimilitude.
Most bits of scenery can also be examined, prodding several different lines of description from Aya. That is easily more detail than most old-school adventure games have.
Self-Imposed Challenge: The nature of several New Game+ modes. You don't get access to any of the unlocked weapons goodies, enemies are tougher, and resources are often limited.
There's a Shout Out to Wizards of the Coast in the Game Room in the well. If prompted long enough, Aya will comment that Pierce keeps going on about "Whotsee" (WOTC obviously being the company's acronym) and "Caves & Creatures".
Spoiler Opening: The opening cinematic shows parts of the Cut Scene where the US military storms the Ark facility and easily dispatches the Elite Mooks that you've had difficulty killing upon their release, not to mention the big Kill Sat scene just before the final bosses.
Swiss-Army Weapon: The basic assault rifle can have a number of different attachments that give it different functions, including a grenade launcher, a bayonet, a flamethrower and a laser!
Toilet Humor: With actual toilets in fact. Look at enough of them and Aya will say she needs to get out more.
Wall of Weapons: Dryfield's only inhabitant is an old man who's surrounded much of the town with booby traps and has a miniature arsenal in his shed. He becomes your main weapon vendor for the first half of the game.
Was Once a Man: Most of the monsters in the first game are mutated animals. Most of the monsters in this game, however, are mutated humans. Some of them, like the young woman in the Akropolis Tower's café, even mutate right in front of you.