Based on How to Kill a Monster, book #46 of the original Goosebumps series.
Gretchen and her stepbrother Clark are visiting Gretchen's grandparents, discover a monster trapped in a room of their house, and must figure out how to kill it before it kills them.
The episode provides examples of:
- Accidental Misnaming: Gretchen's grandparents keep calling her step-brother Clark "Craig".
- Adaptational Intelligence: The grandparents are much less stupid than in the book. In the book, they captured the monster when it wandered into their house one day after they stupidly left the front door open while they were out. They kept it locked in a room because they couldn't think of a way to kill it and kept it fed until they could get their car fixed so they could drive into town for help. They never considered simply letting the monster starve to death, kept it secret from the kids, and drove away with the car once it was fixed while leaving the kids in their house with the monster instead of taking them along like they obviously should have. In the episode, the grandfather shot the monster in the swamp and took it back home possibly as a trophy just before the grandkids arrived, and the reason they head into town is to get groceries. Them not taking the kids with them and leaving them in the house is justified since they had no reason to believe they would be in danger. The monster only awakens as they leave.
- Adaptational Nonsapience: The monster doesn't speak in the episode and doesn't appear to be sapient.
- Adapted Out: Gretchen and Clark's dog Charley does not appear in the TV version. Nor do their parents, as the two children are just dropped off at the swamp without them.
- Alien Blood: When the monster dies, it explodes and covers the kids in green slime and guts, some of which is presumably its blood.
- Argument of Contradictions: Gretchen and Clark get into this when they are about to leave the house through the basement. Gretchen accuses Clark of acting like a coward scared of the monster, while she did all the work. Clark replies, "Did not!" and she counters, "Did too!" They keep going back and forth on this, until their tirade is interrupted by the monster appearing in the basement.
- Captain Obvious: After tricking the monster into falling down the broken stairs, Gretchen tells Clark to hold on, just as he's doing so.Clark: I hadn't thought of that!
- Ill-Timed Sneeze: Narrowly subverted. When hiding out from the monster in the kitchen pantry, Clark starts to sneeze, but Gretchen clamps two fingers on his nose to stop that.
- Now You Tell Me: Clark says this after he and Gretchen read the second letter after killing the monster, explain that they have a monster trapped inside and warn them not to let it out.
- No Kill like Overkill: The monster not only dies, but explodes immediately afterwards, leaving no doubt on the kids' minds that the monster is truly dead.
- Swamp Monster: The episode keeps most of the plot but changed the monster itself. Instead of a green, swamp-dwelling bigfoot, it's a nasty, yellow-colored reptile with a head like a vulture.
- Too Dumb to Live: When cornered by the eponymous monster, Clark tries to fend it off by sticking his hand in its mouth. Luckily for him the monster is allergic to humans and promptly dies, otherwise he would have been lunch.
