These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Critical Research Failure: In "Speed", the earthworm is stated to be "the fastest thing on no legs". That title actually belongs to the black mamba.
Nightmare Fuel: The episode "Horrors", epsecially the winner (parasitic worms)- some can penetrate through your skin, and then live inside you!
In "Odd Couples", the Greenland and Pacific sleeper sharks are sluggish in cold water, so a small bioluminescent bloodsucking copepod attaches itself to the eye and acts like a fishing lure (which also blinds the shark). Yep, having a parasite for an eye!
"Body Snatchers": Toxoplasma, hands down. No wonder it won in this category.
The fate of the female sea louse in "Mothers"; she gets dragged into a cavern by the male, who pretty much rapes her, gets pregnant with practically a thousand squirming babies who eat her alive from the inside out and then burst out of her, killing her in the process.
Tear Jerker: In "Mothers", the fate of the mother octopus. She starves herself for months keeping her eggs safe and when they hatch she's so exhausted that she can't defend herself when a predatory fish arrives. And she only won number two.