T.D., in Mrs. Clusky's chair, explains that the vocabulary is about school, only to be told off by Mrs. Clusky. Then, it cuts to her reminding her students about their report on animal behaviour. She then explains that she will be away for the rest of the week and leave a substitute in class, so on the way home, T.D. and Helen wonder what this substitute will be like, having gotten weird substitute teachers in the past.
When they get to the Lorraines' house, T.D. says that Martha would make a good substitute and he and Helen joke about it. Then, he realises that he's accidentally picked up the sign-up sheet for the substitute teacher (since his mother is the vice principal) and he writes down Martha's name (adding in Helen's last name). He only intends this as a joke, but because the other substitutes are sick, she gets hired.
She goes to school, excitedly anticipating being a teacher, but the janitor doesn't let her in because she's a dog. She sneaks through the back window and sits in Mrs. Clusky's chair, surprising the students. Martha tries to take attendance, but because she can't read, she just has everyone say if they're present. Meanwhile, the janitor becomes angry when he finds a strand of Martha's fur on the floor.
Martha asks what the students have been learning, and Helen reveals that they have reports, but this again causes trouble since Martha can't read. She has the students read to her to compensate, while the janitor finds more hairs. While Martha is dissing Helen's report on cats, T.D.'s vice principal mother finds the janitor and tells him that somebody threw up in the art room, but he's more interested in tracking Martha down.
T.D. forgot to write his report, but he decides to choose dogs as his animal of study. After he gives his inept oral report, she has the students applaud by acting like dogs. The janitor sees Martha and grabs T.D.'s mother, who has no problem with Martha teaching. When T.D.'s mother (whose name is revealed to be Mrs. Kennelly) sees Martha teaching a lesson on dog behaviour, she does an imitation of Courageous Collie Carlo, but this embarrasses T.D.
On the way home from school, Helen and T.D. complain about Martha's incompetent teaching. At the Lorraine house, Helen sulks, and Martha asks her what's wrong, so Helen admits she doesn't like having Martha as a teacher. That night, Mrs. Clusky somehow senses that something is amiss, so she comes back to school the next day as Martha resigns.
This episode provides examples of
- Aesop Amnesia: Martha threatens Helen with a bad grade for her report on cats despite learning not to discriminate against them in "There Goes the Neighbourhood".
- Amazingly Embarrassing Parents: T.D. finds his mother being a vice principal embarrassing, especially when she pretends to be a dog and a frog.
- Bait-and-Switch Sentiment: Zigzagged. The janitor opens the door, Martha thanks him, and he claims that he wasn't opening it for her but needs fresh air instead. However, he seems awkward, so he may have been lying.
- Bread, Eggs, Milk, Squick: The lessons Helen and T.D. joke about Martha giving are dog paddling, catching tennis balls with teeth, digging for bones, and drinking from the toilet.
- Breath Weapon: T.D. draws a substitute teacher breathing fire.
- Catapult Nightmare: Mrs. Clusky sits bolt upright and gasps after having a nightmare about her students growing tails and fur.
- Character Tics: One of the kids' previous substitute teachers had a habit of sniffing her sandwich, and another had a habit of tapping.
- Cloud Cuckoolander: One substitute teacher sniffed her sandwich for no reason and another rapped a lot.
- Comically Missing the Point:
- When the janitor doesn't let Martha in and points to a sign of a dog under a "no" sign, she responds, "That dog doesn't look anything like me."
- When Martha is trying to take attendance, she's illiterate so she can't read the names... so she has all the absent students say, "Absent", not realising they wouldn't be able to.T.D.: "Her methods are unusual and they make no sense."
- Contrived Coincidence: Martha only gets hired because four other substitutes coincidentally happened to fall sick around the same time.
- Flashback: When T.D. says that his class always gets weird substitute teachers, we see four previous substitutes. One of them yelled a lot, one of them sniffed her food, one tapped a lot, and the fourth had a habit of rapping.
- Heroic Dog: Discussed when Martha says that dogs are used by search-and-rescue teams.
- Hollywood Chameleon: Alice says that chameleons hide themselves by changing colour, when actually the colour-changing is an emotional response.
- Inexplicably Awesome: It's never revealed how Mrs. Clusky realised things were going awry.
- Lame Pun Reaction: Downplayed. While T.D.'s classmates laugh at his "ruff" pun, Mrs. Clusky frowns, though perhaps this was more for joking in class than because it was a pun.
- My God, What Have I Done?: When Helen reveals that she disliked Martha's teachings, she feels guilty.
- No Animals Allowed: The janitor doesn't allow dogs in the school, so Martha has to sneak in.
- No Indoor Voice: One of Helen and co.'s past substitute teachers yelled a lot.
- Out-of-Character Moment: T.D. finds his mother's animal impersonations embarrassing despite usually not getting embarrassed and enjoying wacky things.
- Out Sick: The reason Martha got hired was because all the other substitute teachers were sick.
- Pun:
- T.D. jokes that animal behaviour sounds like a "ruff" topic for a school report.
- When Martha sneaks through the window, she calls it "dogged determination".
- She later jokes that being a teacher is no "substitute" for being a friend.
- Race-Name Basis: The janitor calls Martha "Dog" and "Mutt".
- Sadist Teacher: T.D. imagines the substitute teacher as breathing fire and yelling at his students to fear him.
- The Scapegoat: Helen's classmates blame her for Martha's bad teaching because Martha is Helen's pet.
- Skewed Priorities: The janitor flips over a few dog hairs, but doesn't seem to care about vomit on the floor.
- Speak in Unison: The students say, "Present!" in chorus when Martha tells everyone who's there to say it.
- Split-Screen Phone Call: Mrs. Clusky and Martha are seen on a split screen when they talk on the phone.
- Stock Animal Diet: Helen gives digging for bones as a lesson Martha might teach as a substitute teacher.
- Toilet-Drinking Dog Gag: T.D. jokes that if Martha was a teacher, one lesson she'd give would be in lapping water from the toilet.
- Undying Loyalty: Discussed when Martha and T.D. both give loyalty as a trait of dogs.
