"I Have Kind of a Short Running Time, Which Some Find Charming"

It is a fact that a television programme has to meet a set running time, and sometimes it falls short, and one of those programmes is The Simpsons, leading to the astonishingly obscure quote reference in the title of this article. But what to do if you just can't get the programme up to its requisite 22 minutes? There are three main methods of padding the episode out I've identified, which I will now outline for you.

Method 1: Having a longer than usual title sequence.
One way of telling a show is running short is if the show goes into its full title sequence at the beginning. This is particularly true of the modern era, which frequently goes for what is known as the short, 'clouds-to-driveway' version of the opening. There is then an extra bit of padding they can go for: a longer than usual couch gag. Unquestionably the most famous of these was the 'circus' couch gag, which from seasons 4 to 13 was the go-to one to use if an episode was running short; it saw use on a record-breaking eight episodes from 1992 until 2002. The show later branched out with increasingly elaborate and even longer couch gags, with their ever-increasing length becoming something of a sticking point for fans. A more recent innovation with the very long couch gags is to get a 'guest animator' in to them; take, for example, this Don Hertzfeldt gag from a few years ago, which runs to a full two minutes! Two bloody minutes! Take out the adverts and that could be as much as a tenth of the entire episode!

It would be remiss of me not to mention some of the longer couch gags I do like, though; the Powers of Ten one that was in use in the mid-noughties is thoroughly impressive, as is the Evolution of Homer.

Method 2: Dragging out a joke for longer than necessary.
I think this link sums this method up quite nicely. It's actually more complicated than it seems; according to showrunner Al Jean on the commentary, the goal was to drag the joke out for so long that it stopped being funny, and then for even longer so it started being funny again. Exactly how many rakes you should walk into is an exact science.

("Cape Feare" is possibly the pinnacle of this entire article; the producers also deployed the standard tactic of having a full opening sequence with the circus couch gag, increased the rake sequence from one to nine, added an Itchy & Scratchy cartoon, and even then it's still one of the shortest episodes in the show's history.)

Method 3: Adding an extra short to the episode.
"The Adventures of Ned Flanders" is a perfect example, and the only one that really comes to mind in the show's classic era. A more recent episode added a "Simpsons Show's Too Short Story", which is three times the length of Ned's mini-show, but hey, at least they're taking the opportunity to be creative. The 'stingers' they've taken to inserting between the end of the last act and the closing credits in recent years have smacked of this, too, and occasionally feel really out of place.