Animation takes dedication, hard work, and a lot of people that must ultimately love it enough to put up with it. With all that time spent working, it's understandable that the artists would want to point a mirror on themselves and vent their frustrations, share their fantasies, or joy of the medium with the viewer.
So now, in absolutely no particular order, a list of (quite meta) cartoons about making cartoons!
Starting off the entire series with a fourth wall breaking "origin story", Bugs Bunny narrates from a picture of himself hanging on the studio wall about how the series was created. Buster and Babs walk you through the making/creation of the series from their perspective as cartoon characters. From being given life by the artist, to holding literal auditions for other characters. They write scripts for episodes and are all set to help the artist pitch the new show to the studio to be picked up.
But when Montana Max steals the scripts, Tiny Toon Adventures becomes The Montana Max Show. To save their show Buster and Babs need the help of more seasoned Warner Bros. characters!
A more tongue-in-cheek approach to the process, Stimpy tries to create a cartoon to show his hero, the great, "godfather of all animation", Wilbur Cobb. Ren wants to help with it, but doesn't know how to draw (or even make coffee), so Stimpy offers him the job of a producer. Which he explains as the guy that tells the artist what to do, makes all the changes, and then takes all the credit when the cartoon is done. Ren, of course, sees this as a great opportunity, and starts bossing Stimpy around and basking in all the "success".
The cartoon Stimpy ultimately makes after countless days of grueling work is interesting; to say the least (as is Wilbur Cobb). But it's still pretty good for a cat with little to no previous work in the field.
Both episodes use the in-universe cartoon series, Itchy & Scratchy, as a way to commentate on areas of creating an animated series.
"The Day the Violence Died" is about the fictional cartoon series and who actually created it. Mixing allusions to classic silent era style animation and playing with the way production companies sugar-coat stories of how characters get created, this episode takes Bart on a quest for justice to the man that he is sure actually created the character, Itchy the Mouse.
"The Front", inspired by the true story of three 13 year old girls who sent a script they wrote of Tiny Toon Adventures to Warner Brothers (that was made into the episode "Buster and Babs Go Hawaiian"), this episode features Bart and Lisa writing their own episode of Itchy & Scratchy and sending it to the studio with major success as staff writers under their grandpa's name who is unaware of what this is all about.
Honorable mentions are: "Itchy & Scratchy & Marge" (S2E9) and "The Itchy & Scratchy & Poochie Show" (S8E14).
As a series that takes things to extreme possibilities, of course the writers would include a fantasy about making cartoons easy! As fans of the show already know, the two brothers, Phineas and Ferb, do something big every day of Summer vacation. In this episode they're inspired by their father's favorite show from when he was a child and build their own animation studio. With help from their friends, they create Team Improbable. Using technology to do the work for them, it makes things effortless!
Although, not the most realistic approach, it makes every other example look impossible and impractical!
Along with the previously mentioned Ren and Stimpy episode, this is a more realistic portrayal while still being a bit tongue-in-cheek. When the Bighead's son, Ralph Bighead, the creator of a cartoon series called The Fatheads just wants out of his studio contract, only to find out the studio wants a whole new series from him, he has the brilliant idea to have Rocko and his friends create the new series for him, knowing that it would be so horrible, the studio would have to drop him; leaving him to fulfill his dream of creating the world's largest still-life.
Giving the friends a book called, "7,291 Simple Steps to Making Animated Cartoons", they are left to their own devices to come up with what they think would make a good cartoon.
What comes out of their ideas is a series about deli meat called, Wacky Delly. Spelled wrong, so you can guess how good their work turns out! But what couldn't be guessed is that it's a...success?