The season five premiere of "Adventure Time."
Patricia Collura The season five premiere of "Adventure Time."

While the vast enthusiasm for shows like "Breaking Bad" and "Mad Men" have lead the argument that television has entered a golden age of mature storytelling, animation has always thrived in the format with broad appeal indicative of different expectations that liberate the form. Even before "The Simpsons" proved the viability of adult-oriented primetime animation, "Looney Tunes" demonstrated the ageless appeal of slapstick comedy and that visual humor has the capacity to entrance viewers of all ages with a more complex set of access points. ("What's Opera, Doc?" can please everyone from a seven-year-old who may find it delightfully colorful to a 50-year-old who can appreciate its take on Wagner's operas.)

READ MORE: The original 'Adventure Time' short on Criticwire

"Adventure Time"
"Adventure Time"

Both "South Park" and "Family Guy" fully exist in the modern framework of adult-oriented animation pioneered by "The Simpsons," but Cartoon Network's "Adventure Time" more clearly represents the progress of the medium: Irreverent and narratively engaging, it's the ideal testament to animation's glorious pliability in an commercial arena otherwise defined by restrictions. With the start of its fifth season last night, "Adventure Time" once again proves that it's one of the most inventive shows on television.

Creator Pendleton Ward's program began as a beguiling animated short that quickly went viral in 2008; the resulting show neatly expanded on the initial trippy appeal, and continues to evolve in surprising directions. The basic plot follows an adolescent boy named Finn and his stretchy talking dog Jake, who live in a fantastical post-apocalyptic world filled with odd, funny creations like the dyspeptic Ice King and the Bubblegum Princess. (I could list more of them here, but you're better off sifting through the concise episodes to understand the bizarre creations Ward has developed.)

READ MORE: Is Adult Swim Stuck in a Rut of Nostalgia Bait?

While random, frequently adorable and effusive in that familiar Saturday morning cartoon way, "Adventure Time" also constantly -- and with increasing frequency in its later episodes -- toys with an incredibly sad subtext: The world has been destroyed in something called The Great Mushroom War. Everything in roommates Jake and Finn's island the Land of Ooo is haunted by isolation and even death. Their parents vanished long ago, and while the boys apparently enjoy their showdowns with the Ice King, his backstory as a scientist partly responsible for destroying civilization hints at a much darker history that the spirited nature of their encounters only partially covers up.

Adventure Time 3

The cheery songs and vibrant artwork remain sincere while challenging the backdrop at the same time. The subtext of "Adventure Time" calls to mind "Calvin and Hobbes": Through friendship and playtime, the characters seemingly deny the bad vibes their surrounding world invites. The show's a testament to the prospects of cracking jokes when nothing seems funny anymore. Needless to say, viewers can learn a lot here no matter how much life they've lived.

Ward's playful, stream-of-conciousness approach to each 11-minute episode has turned his show into fodder for college stoners hip to its random exposition, but there's a lot more at work in the steadily growing atmosphere. Last night's season five premiere, entitled "Finn The Human & Jake The Dog," provided an interesting creative challenge for Ward and his team: a prolonged running time of half an hour, which basically amounted to a double episode.