Blob Monster: A mid-boss in Evergreen Chemicals, a sentient slime that takes the form of a skull. It shows up at the end of the level as well.
Bus Full of Innocents: NON actually has an armored school bus with gun turrets on the roof and in the windows to transport their hostages to a "Reprogramming Center." In Egypt.
The Can Kicked Him: Hang a leftnote or right, depending on which way the screen scrolls at the beginning of the stage once you enter Club X. You'll get to ambush some hapless NON troopers in the toilet stalls. (As well as an embarrassed bassist. Sorry, Tom.)
Chased by Angry Natives: A hilariously racist pack of tribesmen with masks and spears. The game justifies it slightly by stating they're under NON's mind control.
Elite Mooks: Skatetroopers are more intimidating then their yellow brethren, brandishing a riot helmet, a ballistic shield, and a voice like Darth Vader. They are highly vulnerable while moving, however, and will slip and fall. You should save your CDs for these guys; they can be troublesome. Also a threat are Yellowjackets, which take a bit more punishment, and Berzerkers, who charge at you with throwing knives and machine guns.
Evil Brit: Helga barks out threats in a cockney accent and dresses like a Sex Pistol - which is odd for an authority figure promoting cleanliness and order.
Golden Snitch: If you find all five band members and beat Helga, you get to go backstage and grab "Mammy Award" trophies. Each one adds 50,000 points to your bonus, which in turn is multiplied by 6 for finding everyone. Your final bonus can easily run into the 12-15 million range and end up being over half your total score.
The game isn't very clear what you're supposed to do in certain battles. Such as the bartender who chucks grenades at you (you have to shoot the sign above him), the centipede boss (you have to keep it back during the chase then destroy the bridge when you reach that point) or the battle against Helga (you have to position her in front of the throne then blow her into it).
Additionally, finding each member of Aerosmith (for the score-multiplying wings that unlock a bonus room at the end of the game) is also frustrating. You have to take an exact set of actions to find them, and you only get one shot for each. With one specific exception, it's nearly impossible (if not outright impossible) to find a member by accident:
Steven Tyler appears on an alternate route that requires you to destroy a pair of fish with CDs and then break a mirror after reaching a certain point in the Lounge of level 1.
Brad Whitford actually has a map in the level (Pacific Rim) showing where he is, but getting to him is annoying. You have to go to a specific gate, shoot a box, shoot an arrow sign that becomes exposed when the box is shot, and then quickly shoot the sign again.
Joe Perry is located in a secret room inside another secret room accessed via a secret elevator (specifically, he's behind a grate in a room full of hostages) in the Amazon.
Marathon Boss: All of them, save for that insectoid thing in the Amazon stage (which only needs a gimmick to be beaten). They need an ungodly amount of hits to be taken down, and don't even stop shooting at you while they're being punished. Notably, the armored school bus has a time limit to be destroyed, but it can take so much punishment, you sometimes wonder how is it even possible to beat it. Not that it can't be done, mind you, it's just that hard.
McNinja: Sure, why not? They dress like Power Rangers, natch.
Metal Scream: Steven does his occasionally in response to the ongoing action.
The New Order Nation's logo looks like a parody of the Nine Inch Nails logo.
Slave Mooks: Berserkers are ex-musicians who have succumbed to NON brainwashing. They are among the sturdiest enemies in the game, and hurl axe-shaped guitars (geddit?) at the screen.
Spiritual Successor: To the Terminator 2 shooter by the same developer. Several missions are identical, including the chopper shootout and the bus chase (both lifted from the HK battles in T2's ruined future).
The Syndicate: The New Order Nation has shell companies all over the world, including Evergreen Chemicals and an outfit called KemmiTech. Their main function seems to be experimenting on scantily clad babes.
Somewhat justified in the labor yard, where the hostages are upgraded to... denim hot pants.
Twenty Bear Asses: You have to find all five members of Aerosmith to get the real ending. The members of the band are ridiculously hard to find, and you only get ONE chance to find each of them. These are five particularly annoying asses.
Not getting all five asses, in this case, results in quite the A Winner Is You situation. To sum it up: "You beat the game except you didn't, go find the members of Aerosmith!" All of the members of Aerosmith are hidden except for Brad Whitford, who actually has a map telling you where he is... but he's ridiculously difficult to reach. (As mentioned above, Tom Hamilton can be rescued in the very first level if you're quick to make a left [or right] turn upon entrance to Club X. The other four? Good luck.)
Writing Lines: "Helga's No Nos." An amusing way of outlining the game's goals.
NO!Shooting power-ups NO!Looking for Aerosmith members NO!Tattoos
You ALL Look Familiar: Kerri Hoskins, best known for mocapping Sonya Blade in Mortal Kombat 3, plays Mistress Helga. She also posed as the thong-clad cage dancers/chain gang prisoners/lab test subjects throughout the game.
Zerg Rush: NON troopers have the resiliency of tissue paper. Trouble is, they never stop coming.