Parent Ex Machina

In many sitcoms and teen dramas where young persons are the focus of the show, parents (and other adult authority figures) serve no purpose in the show other than to swoop in at the last second to either deliver An Aesop or to ensure that Can't Get Away with Nuthin'.

After a while, you start to wonder how exactly they keep catching the kids, given that they seem to have absolutely no involvement in their lives otherwise.

Few shows adhere strictly to this model: in many, the adult steps out of this role on rare occasions for a A Day in the Limelight episode. Another alternative is the half Parent Ex Machina; the show typically employs Two Lines, No Waiting, with separate storylines for the adults and the kids, which interact only at the last moment to deliver An Aesop or catch the kids. Many a Double Aesop is forged this way.

Essentially one step up (or down, depending on how you look at it) from Adults Are Useless. Compare and contrast Parents as People, where the parents are almost too busy getting Character Development to actually do any parenting.

Examples of Parent Ex Machina include:

Anime and Manga

Ichigo's father in Bleach comes down on him really hard at first for tiny slip ups but as soon as he becomes a Shingami lets up and Ichigo gets away with everything (because being grounded would be both inconvenient and ineffective for someone who can leave his body) this is partially Justified in that his father knows about his powers and supports his actions, even if Ichigo doesn't know that.
- Ishida's father Ryuken is... very unloving towards his son. That is, until his son loses his powers and nearly gets killed by hollows, then he steps in to save his son and restores his son's powers. He still acts like a total dick to the kid, though; that spoilered bit involves driving Uryu to his physical extremes and then shooting him in the heart.

Literature

Kid Lawyer, by John Grisham.
The Face on the Milk Carton has shades of this. The heroine suffers significant angst through the story, before informing her parents, who fix everything.
- To be fair, her angst is because she's not sure she can trust her "parents", once she comes to believe that they kidnapped her as a small child.

Live-Action TV

Boy Meets World, especially in its early seasons. In the later seasons, Mr. Feeney's character became a lot more substantial, but the parents were all but written out.
Leave It to Beaver. Quite a lot, just when it looks like Wally and Beaver will get away with whatever mild infraction they've committed, some acquaintence of the parents will phone and say they happened to spot the boys doing whatever it was they shouldn't have done, and they just thought they'd call and make sure everything was OK. This can get pretty annoying, especially if the kids had already dealt with the consequences of their mistake on their own; it appears to be tacked on just to reinforce that they Can't Get Away with Nuthin'.
The Brady Bunch.
Saved by the Bell: We only see any actual parents a handful of times, and Mr. Belding's only purpose in the show is to show up at an inconvenient moment to say "Hey hey hey, what is going on here?"
Diff'rent Strokes.
Facts Of Life.
Just The Ten Of Us.
The Many Loves of Dobie Gillis.
Happy Days and the Cunninghams, particularly Howard.
Full House.
Mr. Belvedere.
Growing Pains.
Gilmore Girls particularly in its recent seasons, though subversion since the parent-child relationship is so often reversed.
Family Ties.
An episode of Star Trek: The Original Series had a variation on this. Trelane, who seemed to be a Sufficiently Advanced Alien, turned out to merely be a naughty child. His "parents" (who appeared as blobs of energy) arrived just in time to save Captain Kirk and punish their boy.
- A similar situation happened in the Buffy the Vampire Slayer episode about her roommate from Hell. The girl, as it turned out, was a demon who "snuck out" to spend time with the mortals. Her father "rescues" Buffy from having to interact with her anymore, at which point, Buffy moves in with Willow. Being dragged back to her dimension, the demon grumbles: "When will you stop treating me like I'm nine-hundred?"
  - Buffy herself often faced this trope in the early episodes. Her mother was involved in some plots, but very few, and she almost never did anything useful. Often, when she did appear, it was to try to have a heart-to-heart with her wayward daughter about either mundane matters that had no real importance compared to what Buffy was dealing with (although usually it was somehow metaphorically related to the plot), or supernatural events that she grossly misinterpreted. Later, Buffy told her mother that she was the Slayer, which, after the initial shock, improved their relationship significantly.
Hannah Montana

Newspaper Comics

Dennis the Menace.^[context?]

Web Comics

Dominic Deegan. Miranda Deegan is aware that her children are adults, but doesn't hesitate to bail them out if they are in serious trouble. Since she also happens to be one of the most powerful Archmages in the setting she also counts as a Deus Ex Machina.

Western Animation

Recess.
Kim Possible.
- Your Mileage May Vary, as Kim's parents are at times very supportive of their globetrotting, crimefighting daughter.
Spoofed in South Park, which usually has one of the children delivering the Aesop to the adults.
In many episodes of Rugrats, probably a majority, Adults Are Useless from start to finish. But there are also many episodes where the parents will suddenly catch onto the Devil in Plain Sight misbehavior of Angelica, or otherwise do something useful to resolve the plot at the end of the episode.