In an old house, Martha and T.D. are dressed up as stereotypical detectives. However, this turns out to be in T.D.'s imagination, and he snaps out of his daydream when Janice tells him to take some recycling to the junkyard. So, he goes, and Martha comes too, but when he shows her his collection of junk he keeps at the junkyard, the trophy he won in the last episode is unaccounted for. They tell the owner of the junkyard, Joe, who reveals that his clipboard is missing too. He soon finds it, but then he finds a bunch of copper missing.
T.D. and Martha wonder what's happening on the way back, when they pass some display TVs that are playing a show in which someone robbed his own store. This causes T.D. to wonder if he stole his own trophy while sleepwalking. They search the Kennelly house, but find no sign of the trophy, so he decides he didn't steal it after all.
At the pool, T.D. and Martha ask Helen and Alice about the situation, but Alice is more concerned with the fact that he put their trophy in the junkyard. At Alice's house, she asks Ronald if he took it, but he denies it, pinning the blame on one of T.D.'s friends. T.D. wonders if he still stole it in his sleep.
He and Martha go to the junkyard again, where Joe hands them a DVD. They go to T.D.'s house and watch it, and it's an anti-pollution PSA. T.D. learns from the PSA that copper is valuable, but still has no clue who stole it. He wonders if he did do the robbery in his sleep, and so has Martha sleep in his room and tells her to not let him out of his room if he sleepwalks "again". However, she falls asleep while trying to watch him.
The next day, they go back to the junkyard, and Joe reports more stuff stolen. T.D. sees some of his footprints and wonders if that means he came there in his sleep, but they turn out to just be the prints he'd just made that day. Then, Martha finds another junkyard, which contains everything that had been missing.
They tell the police, and T.D., still thinking he did it in his sleep, begs the chief to arrest him. However, the police chief doesn't believe T.D. did it. That night, the police chief, T.D., and Martha go to the junkyard, where they find a man stealing more junk with a crane. The police chief orders him to exit his crane, and it turns out to be the man from the PSA.
This episode provides examples of
- Alliterative Title: The Missing Metal Mystery.
- Amusing Injuries: T.D. bumps his head while searching under his bed.
- Astonishingly Appropriate Interruption: T.D. asks himself why anyone would steal the trophy and the copper, and then the scene cuts to Joe saying, "Oh, lots of reasons".
- Breaking the Fourth Wall: In-Universe, Joe and the other guy talk to the viewers in the PSA.
- Chekhov's Gunman: The guy from the anti-pollution video turns out to be the metal thief.
- Continuity Nod:
- T.D. still has his junk collection from "T.D. the Pack Rat".
- One of the missing things is the trophy T.D. and Alice won in "Wagstaff Races".
- Daydream Surprise: The first few moments of the episode turn out to be in T.D.'s head.
- Green Aesop: In-Universe when T.D. and Martha watch an anti-pollution PSA.
- Half-Dressed Cartoon Animal: Martha is seen wearing a coat and no pants in T.D.'s imagination.
- Imagine Spot: T.D. briefly imagines stealing his own trophy.
- Insane Troll Logic: T.D. thinks him stealing his own trophy in his sleep is the only option because he knows it wasn't a monkey (since he called the zoo) or a robot (since no one's seen any robots).
- Kid Detective: T.D. investigates (albeit somewhat ineptly) the theft of some things from the junkyard.
- Mistaken for Thief:
- Played for laughs when T.D. wonders if he stole the metal from the junkyard, while sleepwalking.
- Alice, at one point, wonders if Ronald was the thief (since he narrowly missed winning the trophy), while he wonders if it was Helen, Alice, or Martha.
- Mystery Episode: This episode involves T.D. and Martha investigating the disappearance of some stuff from the junkyard.
- Pun: When Janice says that T.D. is reducing waste, he asks if he's getting thinner (as a pun on "waste" and "waist".)
- Running Gag: T.D. keeps suggesting that he was the one who stole the trophy and the copper (in his sleep).
- Silly Simian: At one point, T.D. wonders if it was a monkey who stole the trophy and copper.
- Sleepwalking: Discussed when T.D. wonders if he stole his own trophy, with the addition of the copper from the junkyard, in his sleep.
- Stock Costume Traits: Martha and T.D. dress as stereotypical detectives in trench coats and deerstalker hats.
- That Makes Me Feel Angry: The guy in the anti-pollution PSA says, "Wow, I feel bad!".
