* FridgeBrilliance: In the final level, as your PlayerCharacter gets closer to the FinalBoss, you start fighting lots of oversized '''viruses'''. It may seem weird, until you [[AllThereInTheManual find out from the backstory]] that is was a virus bomb that caused the entire mess.
* GoddamnedBats: The cave stage has them. Although they don't fire at all, they tend to appear in groups. And if they fly off the left side of the screen... they come back in facing right, and try to fly into you again!
** One of the enemies found in the final stage disables your AttackDrone by encasing it. Until your drone can shoot its way out, you'll have to rely on your regular weapon! Thankfully, you only encounter about 3-4 of them or so.
* NightmareFuel: The biological design of the enemies and bizarre stages mean there's quite a lot of creepy stuff. The stage 2 boss in particular... (it's a giant rat-tail maggot)
** And those walking hearts that shoot ''[[BloodyMurder blood cells]]'' at you!
* ThatOneBoss: Many people consider that shark/gulper eel hybrid to be the toughest boss, and the constant stream of Mooks [[FlunkyBoss that come with him]] don't help. [[ThreateningShark Everything Is Even Worse With Sharks]], it seems.