Why writers of cult TV animations love a show-within-a-show

"Back in the 90s", go the opening lyrics to BoJack Horseman, "I was in a very famous TV show". That show was, of course, Horsin' Around, a spoof of US family sitcoms of this era like Fuller House.

BoJack has struggled to adapt to life after Horsin' Around, in which he starred as a horse who adopted three human children. (If you've never seen the show, it's set in a world where humans and anthropomorphised animals live side by side).

BoJack frequently watches old episodes of Horsin' Around for comfort. His reliance on this is key to understanding BoJack Horseman as a show, argues Esther Breger in Slate.

She writes: "In the Season 3 finale, a self-isolated BoJack watches himself deliver a heartwarming message to his young ward... You get the sense that BoJack, who has failed everyone in his life, wishes the real world could be that simple."

Itchy and Scratchy have been part of The Simpsons universe since the very beginning, appearing alongside the family on The Tracey Ullman show.

David Silverman, who produced and directed for the show, argues that the cat and mouse show is a comment on cartoon violence.

He said: "There's not the quick recovery that you normally associate with cartoon violence. That's the big joke behind the segments. It's an ironic commentary on cartoon mayhem in the sense that it's taken to a more realistic level. The kids on The Simpsons are laughing at it, and we're laughing too, but part of what you're laughing at is the over-the-top excessiveness of the violence."

But the commentary was taken to another level in the season eight when there was an episode centred around the introduction of a new character, Poochie, a dog with "attitude", in order to inject energy to a struggling show, much to the frustration of the Itchy and Scratchy production staff.

Silverman says this was inspired by suggestions that the showrunners received from executives at Fox. He said: "Fox requested that they add another character to The Simpsons. They said, 'Well, we introduce new characters all the time'. And Fox said, 'No - to the family'. The reason shows like Married... With Children add the bratty cousin is because the other kids are turning into adults. You don't have that problem in animation. 'No, no, it'll freshen up the act.' "

There's a whole episode of Rick and Morty based around extremely strange TV shows. In Rixty Minutes, Rick installs a device which allows the Smith family to watch any possible channel in any possible reality.

Unusually for an animated series, the episode was based on improvised dialogue from creators Dan Harmon and Justin Roiland. Vulture writer Daniel Kurland heaped praise upon its experimental spirit.

He wrote: "A lot of this episode’s success is due to coasting off of Justin Roiland’s fumbling energy and simply how much fun these guys are having with their nonsense.

"One of the truly amazing feats within Rixty Minutes is seeing the artwork that these animators come up with based off of Roiland and Harmon’s improvised tangents (their work in the Turbulent Juice ad is particularly inspired).

"The animators were given free rein to do whatever they wanted with the nonsense that’s being spouted and it amounts to a prime example of how funny the animators (or art department) of a series can be, in addition to the writers. This is as much a showcase for them as it is the writing staff."

In PTV, we follow Peter Griffin as he launches his own TV station. The tastefulness of his output is highly questionable, with shows including Sideboob Hour, which he calls "a wonderful look back on all the partial nudity network television used to offer."

But the show's creative team were making a wider point with the episode. After Janet Jackson's 2004 Superbowl 'wardrobe malfunction' the Federal Communications Commission – the body which regulates the US media – introduced new rules which the team behind Family Guy believed to to be verging on censorship.

The PTV episode of South Park was in part a reaction to that, according to revealed Seth Macfarlane, the show's creator, in a discussion about story development.

He said: "In the case of 'PTV' it came out of rage. Rage over all the crap we have to deal with since Janet Jackson showed her 67 year old boob."

The Terrance and Phillip Show is something of a proxy for South Park itself.

Matt Stone, one of the show's creators, says he and fellow creator Trey Parker have much in common with their creations.

He said: "They are kind of like us in that they love fart jokes. Terrance and Phillip is our answer to the critics who said that South Park was nothing but fart jokes. Oh Yeah?! Well HERE is a show that is really all fart jokes!"

Terrance and Phillip's spouses are also used to make a serious point in the show. In season 13, they marry Katherine and Katie, with the female characters' delight in their own bodily functions serving to contrast the disgust the male characters feel, thus highlighting the double standards between the sexes.

Daria was the sarcastic queen of MTV in the 1990s.

Sick Sad World, the show that characters watched within the show, was strangely prescient of the type of content that would become a viral hit once social media became a major force in most of our lives.

MTV writer Amanda Bell said that in retrospect it seems like the show's creators Glenn Eichler and Susie Lewis were "trying to brace the planet for what grave ills we were all about to experience".

Items which seemed to predict our content future included monkeys using technology (which would come to life in selfie monkey) and rodent infiltration of human life (such as the infamous pizza rat of New York).