- The Control Voice: The Bible says, "Judge not, for ye shall be judged." If we look beyond the weaknesses of those among us we call feeble, we may find surprising power buried within.
When parasitic worms take over the bodies of the inhabitants of a small town, it is up to a mentally disabled boy to stop them.
- The Control Voice: Mankind puts the strong, the athletic, the genius, on a pedestal. If we treated the less fortunate among us as equals, we would see that they can also become heroes.
- Blatant Lies: Infected!Shiela tries to discourage Howie from using the dynamite to close off the mines by telling him their father (who taught Howie about dynamite) blew himself up. Bear in mind that early in the story, Sheila clarified that their father's death was caused by a cave-in at the mines, not by mishandling of the dynamite.
- BrotherSister Team: Howie and Sheila Morrison work together to rid the townspeople of the ancient parasites.
- Brutal Honesty: When Howie wonders why she's packing, Infected!Sheila says she's "leaving". When he wonders if she's leaving the same way their parents "left", she casually tells him "No, not like mom and dad, they died. I'm just leaving".
- Disability Immunity: The alien parasites are unable to take the intellectually impaired Howie Morrison as a host due to his different brain chemistry.
- Dumb Is Good: Neil Patrick Harris plays Howie Morrison whose mental disability renders him immune to Id-unleashing parasites.
- Dug Too Deep: This episode has a group of miners blast into an ancient cave containing a dinosaur fossil and a crapload of worms that quickly infest the miners and, shortly after, the whole town. Luckily, they hate light and need salt to survive.
- Gaslighting: The second time around, Infected!Sheila does everything she can to make Howie doubt himself, from discouraging him from lighting the explosives to convincing him that she can trust him. She even manipulates him from trusting their father's tutelage on safely handling dynamite by twisting the truth that he blew himself up.
- Hidden Depths: Despite his condition, Howie is intelligent enough to remember how his dad taught him to safely prepare and light explosives.
- In One Ear, Out the Other: A small town is invaded by prehistoric slug-like parasites who crawl into a victim's head through nostrils or earholes and turn them into hedonistic delinquents. A waitress has one slug crawl in her right ear, then much later falls out of her left ear dead, leaving her back to normal. This might have been a mistake but she did come across as pretty ditzy so this might have been a stealth pun...
- Kick the Dog: Infected!Sheila has no reservations about insulting Howie about how he's holding her back and how the one thing he "did wrong" was "being born".
- Orifice Invasion: The prehistoric worm parasites enter (and later exit as they die) through nostrils, mouths and ears. One girl actually has a worm go in her right ear (complete with blood) and at the end of the episode have it come out her left ear without leaving her with any ill effects (other than a great deal of pain).
- Puppeteer Parasite: Prehistoric worms take over a mining town but get defeated by a mentally disabled boy who figures out that they like salt and hate sunlight. They also cause the host to lose all inhibitions.
- Something They Would Never Say: Infected!Sheila's habit of insulting and demeaning Howie is what tips him off that she has a parasite inside of her and he should indeed go ahead with sealing off the entrance to the mines.
- You Are Better Than You Think You Are: After she's freed from her parasite, Sheila lets Howie know that despite what she may have told him, he is indeed a hero. In fact, she remarks that in spite of his condition, he proved just intelligent enough to piece together that sunlight drives out the parasite from their host.