Believe it or not, Adventure Time is growing up, and at a fairly considerable clip. Outwardly, the animation hasn't changed dramatically since the show's finely tuned third season, yet instances of decidedly darker, more mature artistic flourishes appear quite often. The Land of Ooo and its multiple sub-landscapes are more expansive and numerous, more vivid and surprisingly naturalistic in their environmental decor (as much as a cartoon of this kind can be); traces of the post-apocalyptic geography the series outlined and explored at its origin have become increasingly pronounced, with new, more detailed backdrops being ushered into rotation.
In addition, the show's characters feel like they're growing older, at least in terms of their personalities. Most prominently is lead protagonist Finn, whose extremely simple-minded, almost one-dimensional, attitude has blossomed into a young man's vastly complex worldview—and one that can fluctuate on a dime. Hints of the Finn from Adventure Time classics like "The Limit" still exist, yet our hero seems to approach each situation, be it petty or imminently life-threatening, sans the impulse-driven mannerisms that defined him early in the series. His development is clearly heard in the intermittent mid-puberty vocal crackings of Jeremy Shada, who began this project going on 13 and is now capable of obtaining his learner's permit.
Adventure Time's recurring themes and examination of morals have also greatly evolved in its fourth season. The idea of everlasting, all-encompassing love and its accompanying joys and hardships have always been somewhat of a primary focus for series overseer Pendleton Ward and his creative team, but never have the intricacies and ramifications of adoration been pushed to the forefront of Finn and Jake's exploits as they are here. Of the season's first six episodes (seven if you count the "Daddy's Little Monster" portion of the two-part "Return to the Nightosphere" saga as a standalone piece), at least four have dealt heavily with interpersonal unions not strictly described as "friends only." It's frequently astonishing to observe the confidence and wide-ranging appeal with which Adventure Time unswervingly depicts the many stages of infatuation. "Hot to the Touch" finds Finn falling head over heels for a princess literally composed entirely of regenerating fire, an uncomplicated yet vastly pertinent metaphor for the hypothesis that the closer you cherish someone, the likelier they are to singe your soft exterior and the easier it is for them to affectionately melt your exposed heart. "Web Weirdos" and "Dream of Love" both present determinedly adult interrelations through the eyes of the inexperienced Finn, with the former subtly highlighting a couple (giant arachnids voiced by Bobcat Goldthwait and Susie Essman) in dramatic decline amid an unexpected pregnancy, and the latter delving into the societal rift created by the public displays of affection between a tiny pachyderm and a pig (complete with Beat Happening-style musical number). Both cover opposite ends of the relationship spectrum, yet do so with such originality, humbleness, and poise that any viewer, from age six to 60, can find something to identify with.
Besides its fetching, eccentric visuals, the show's dialogue is among the best of any current animated series. Characters never say more than is necessary to get their points across, and each line comes off as remarkably natural, akin to spot-on improvisation, but without the layer of wackiness that can typically bog down cartoons of any permutation. Even as Finn constantly invents fresh words to describe the awesome and the lame, it rarely feels like the writers are attempting to create a meme. In addition to Shada, veteran John DiMaggio continues to hone his craft, instilling a bizarre humanity into Finn's mightily malleable canine sidekick, Jake, which transcends that of not only nearly every other Ooo inhabitant, but most of the longtime voice actor's many other roles (including Futurama's Bender). As Finn's eternal bro and confidant, Jake usually finds himself in the middle of more complicated, morality-driven dilemmas than Finn. Whereas his human counterpart commonly confronts his circumstances with spur-of-the-moment physical actions, Jake's responses are much more emotionally penetrating, his inner turmoil and peculiar thought processes painstakingly laid out for all see. The very charming "In Your Footsteps" is a fine example of this, as a seemingly wayward woodland bear begins to imitate Finn's every affectation, Jake becomes progressively suspicious of the wild thing's intentions, while Finn sees the animal for what it is, labeling it a fascinating party trick. Jake's slippery sanity is something Adventure Time has dealt with in the past to extraordinary results (see last season's haunting "No One Can Here You" for a glaring sample), and DiMaggio's delivery of Jake's panic-stricken sessions is a true testament to the actor's degree of successive theatrical refinement.
Even as it illustrates a slow, stark severance from its lighter adolescent beginnings, Adventure Time still possesses strikingly few faults; the ease with which it has captured the attention of such a sweeping audience is comparable to Genndy Tartakovsky's spectacular animated three-peat consisting of Dexter's Laboratory, The Powerpuff Girls, and Samurai Jack—Cartoon Network classics that lured children in with their colorful exteriors and adults with dashes of sophistication and multiform messages. Ward regularly cites The Simpsons as an inspiration for his work, and while Adventure Time's latest season may not mirror the groundbreaking qualities of that series's fourth year, it assuredly warrants comparison to the Matt Groening game-changer's widespread topicality.