Niche Network

A simple Show Within a Show gag. With the sheer number of television stations available in this day and age, a channel that only has programming which relates to a single hobby or niche can be viable. Think "The Golf Channel" or "Soapnet" for real life examples of this. Naturally, these niche' networks aren't all that appealing to people who aren't interested in the networks' subject matter. Some shows like to exaggerate how uninteresting these channels are to non-hobbyists. They do this by having a character turn to a channel that only runs programming about an unbelievably inane subject 24 hours a day.

The gag works because the channel is boring in two different ways. Even if you somehow manage to find the boring subject matter intriguing, the channel is implied to be repetitive ("We're all X, all the time" or "X, 24 hours a day.). As if that wasn't enough boredom, some shows add to this gag by having an extremely bored sounding man narrate the channel's programming in a bland monotone.

To put it simply, a show you're watching makes up a TV channel. If the gag works, you'll be asking yourself one question about that channel. "Who would watch that boring crap?"

Examples of Niche Network include:

Fan Works

Spoofed in Yu-Gi-Oh the Abridged Series with the Card Games Network, because "a children's card game" is always Serious Business.

Live Action TV

On the Sesame Street segment Elmo's World, Elmo's TV tunes in to these kinds of channels to teach kids.
CSPAN and other networks that focus on Political Programmes are often portrayed this way in kids' shows.
- As are 24-hour News Broadcast channels.
Shining Time Station had the kids introduced to television via Schemer, who showed them such channels as footage of babies crying.
Though not TV networks, the 'guest newspapers' from which Have I Got News for You takes some of its fill-in-blanks headlines for the final round are basically this trope. And they're all real.

Radio

The Martin Molloy radio show did a fake ad for its fictitious pay TV network which included "the Hat Blocking Channel. All hat blocking, all the time. <beat> We don't know what we were thinking either."

Web Animation

Siblings had "The Pointless Channel."

Western Animation

Garfield has this as a common gag.
- The gag also appeared many times in the 1990s animated adaptation, Garfield and Friends. Some examples include "The Potato Channel" (in which a man lists all the different ways to prepare potatoes), "The All Snail Racing Channel", and "The All Lasagna Channel."
Johnny Bravo once caught a glimpse of the "Fish" Network. The channel's content consisted entirely of video recordings of fish swimming. "All fish, 24/7"
- Johnny also once had a bear named "Chronos, The Master of All Time," watch the "Tree Channel" to try and cure his insomnia.
Johnny Test: "The Nutz Channel. We're all nuts, all the time."
Sheep in The Big City had "The Watching Paint Dry Channel."
The Fairly OddParents featured "Teeth TV" and "The Clown Channel."
I Am Weasel had The Airplane Channel, which is pretty reasonable. (This was the gimmick of the real-life Discovery Wings channel before it became the Military Channel.) At the end of a Wright Brothers documentary, the brothers decide to toast with a root beer float, after which the channel inexplicably becomes the Root Beer Float Channel.
- The same episode also showed glimpses of the Cat Shaving Channel, and the Grandma Channel. The Root Bear Float Channel was where Chicken finally decided he had enough, and turned off the television.
This was a running gag on 101 Dalmatians: The Series. Various channels on the pups' TV set included "The All-Dog Network", "The All-Cat Network", "The Gravy Channel", "The Poultry Channel", "Swine TV", "The All-Fashion Network", and various others.
In The Powerpuff Girls episode "Daylight Savings" the Professor gives the girls a curfew. The villains take advantage of this and when the Professor tries to watch TV, all the channels he switches to are discussing how Townsville is doomed. He finally finds one that is talking about something else: the time channel. On this channel, Sonny Dial presents the up to the minute time. This reminds the Professor he forgot to set the clocks back, so he can sends the girls back out to save the day.
From The Simpsons- "Coming up next on The Clock Channel: 6:00."
Rocko's Modern Life has a 24 hour bagpipe station featuring the "All Scottish Show".
Daria featured the Pigskin Channel (a decade before the launch of NFL Network) and a fashion channel.

Real Life

The Puppy Channel.
- In order to give their staff some time off, some networks will play a video of a Yule log burning around Christmastime.
- "That channel that exists to sell knives" aka the Infomercial channel.
Other examples are available in the Networks article.