While thinking back on my post about why sequels suck I found myself focusing on how in general 4-koma adaptations tend to avoid the sucky second season trap. This got me thinking about the various anime versions of four panel manga that I've seen and why I've consistently enjoyed each and every one of them.
The primary reason as to why 4-Koma translates successfully to anime lies in one simple fact: generally there's not much of a story. Now before I start getting irate fans banging down my door trying to explain the infinite complexities of K-On!'s narrative to me, hear me out. By it's sheer nature, four panel manga is set up as a series of short gags, with some kind of punchline each time. That isn't to say that there's no story as nine times out of ten there is an overarching narrative, but it's certainly not the correct format to use for any kind of plot-driven manga, be it serious or comic.
One of the problems with anime adaptations is attempting to comprehensively translate a solid story into an entirely different medium without losing the essence of the source material. Many time this involves cutting out odd details, expanding upon others, or even changing certain parts entirely, and in doing this opens up the anime to criticism from existing fans of the manga. For instance, when it comes to shounen, many of the battles which are punchy and dynamic in the manga lose some of their fizz in an adaptation when they become dragged out. A prime example of this is the battle in Naruto between Orochimaru and the Third Hokage, the manga's pacing works well, but in the anime, it seems like Hiruzen and the snake-tongued maniac spend endless episodes standing still causing the viewer to become frustrated and yell "JUST PULL IT OUT ALREADY!" at the screen.
With a sketch-like nature, this is something that 4-koma doesn't suffer from. While an anime will expand each scene, it manages to keep up a similar pace to the manga allowing the jokes to work just as well as they did in the original. A prime example of this is Azumanga Daioh. To date this remains one of of the funniest series I've seen because it keeps a steady pace, keeps the jokes coming thick and fast, and doesn't become too frenetic.
Another thing that 4-koma adaptations never suffer from is filler. while they undoubtedly contain plenty of padding, it doesn't tend to disrupt the show's momentum. With many adaptations, there's a distinct drop in quality when it comes to filler arcs, for example, compare the piss poor Lurichiyo arc in Bleach with the awesome Hueco Mundo battles, or the short but somewhat dull Rainbow Mist arc and the equally short but far more entertaining Buggy arc from One Piece. Filler in plot-driven shows tends to be more obvious, but because four panel manga generally tend to play out more like a series of slice-of-life skits, additional content tends to be of a similar level. I rememeber reading Hidamari Sketch and being surprised that some of the scenes I'd seen and loved in the anime weren't actually in the manga.
I also wonder if sometimes there's less attachment to having the story in a four-panel adaptation be 100% accurate to the source material as there is with narrative-focused manga. Rarely - if ever - do I see people moaning "but it's not like that in the manga!" about a 4-koma adaptation. People become attached to a story, and if an adaptation alters that, cuts bits out, or doesn't do it justice, there's more room for fan fury - and this is true for all literary to video media adaptations (I remember getting seriously pissed at the omission of Voldemort's family history in the movie of Harry Potter and the Half Blood Prince). However, four panel manga is more about the individual scene and character dynamic than the story as a whole, so I personally believe that if the way the protagonists interact with each other and the style of humour remains the same, it's easier to please - or at least placate - the fans.
Certainly from my point of view, the most successful manga to anime adaptations are those that are from 4-koma (or those that seem like they should be four-panel, but arent - Nichijou, Chi's Sweet Home, Shinryaku! Ika Musume). In not being restricted by a distinct and well-loved plot, these series have more freedom and more opportunity for creativity. They're easy-watching, damn good fun, more often than not leave you wanting more, and offer up that age old rarity: a decent sequel.