While trying to thwart Penguin's robbery of a rare Faberge egg, Batman is weakened by exposure to a toxic gas. He takes shelter in a basement apartment belonging to Sherman, a preteen amateur detective.
Tropes in this episode include:
- And the Adventure Continues: The kid detectives continue solving mysteries in their neighborhood after Batman recovers.
- Batman in My Basement: Trope Namer. The usual "hide from the parents" plotline is waved away by an Ignored Confession in favor of "Home Alone" Antics.
- The Family for the Whole Family: The Penguin and his henchmen are continuously foiled by the local children who have Batman in their basement. This is one of the reasons that the production team does not think very highly of this episode, since they were hoping the series would avoid kid heroes and bumbling villains.
- Humiliation Conga: Capped by the newspaper headline; it's doubtful Penguin showed his face among the Gotham underworld for a while.
- "Home Alone" Antics: The final act has the kids trying to fight off the Penguin and his goons by improvising a defense with the equipment in Batman's Utility Belt. Interestingly, they almost get killed in retaliation by the Penguin (doubly so because they annoyed him into a murderous rage), but this still buys Batman enough time to recover and pull a Big Damn Heroes.
- Hypocrite: Penguin resorts to a hammy comment while calling Batman a ham; pretty blatant there.
- Ignored Confession: When Sherman's mother asks what they're doing in the basement, Roberta answers, "We just saved Batman's life, and now we're hiding him from some bad criminals." The mom's response? "That's good, just don't make a mess."
- Improvised Weapon User: Without his belt handy, Batman is able to hold off the Penguin using a screwdriver, nothing more.
- Kid Detective: Sherman aspires to be one, and then gets the chance to be one in spades.
- Lighter and Softer: The most lighthearted, kiddy episode of the series, and a stark contrast to episodes before and after it.
- The Man Makes the Weapon: When the Penguin draws his umbrella sword, Batman (still injured) picks up a screwdriver.
- Oh, Crap!: "My house! SHERMAN!"
- Something Completely Different: A "lighter" episode in which Batman is actually out of commission for most of the adventure (after suffering a poison gas attack) and a group of suburban kids are forced to protect him.
- Stealth Insult: Penguin to his henchmen: "Gentlemen—and I use the term loosely—let the egg hunt begin!"
- The Unmasking: The two teens almost unmask an unconscious Batman, but Sherman stops them.Sherman: This isn't a game, you jerks!
- Upper-Class Twit: Penguin comes across as one; Sherman's house is rather nice, but the villain claims that ransacking the place "could only improve it."