"Beavis & Butt-Head" returned to television a few months ago, and the boys were essentially unchanged from their '90s origins. But even as they're back on the air, there's a generation of comedy writers who grew up watching their original adventures, and — in the same way that Seth MacFarlane's "Simpsons" love gave us "Family Guy" — who have now tried crafting their own animated comedies about oblivious teenage boys.
 
One of those, MTV's "Good Vibes," actually aired as a companion to "Beavis & Butt-Head," and tonight at 10:30, FX debuts another: "Unsupervised." Created by "It's Always Sunny in Philadelphia" writers Rob Rosell, Scott Marder and David Hornsby, it's about best friends Gary (Justin Long) and Joel (Hornsby), who technically have adult guardians but have essentially had to raise themselves — and who have a fundamentally flawed understanding of the world as a result. (Joel in particular seems very Beavis-like, with his shock of yellow hair and frequent moments where he can't keep control of his emotions.)
 
But what's most interesting about "Unsupervised" — and what kept me watching all three episodes FX sent out for review, even though I didn't find any of them terribly funny — is that Gary and Joel's DIY upbringing hasn't turned them into slack-jawed, hateful morons. Instead, despite having no one to care about them but each other, they are the most exuberant, optimistic characters on television this side of Leslie Knope on "Parks and Rec." They have no idea what they're doing, and tend to make the worst possible choices, but all their mistakes come from a good place.
 
In one episode, for instance, the boys are introduced to a new kid at school who assumes they can help her find drugs, and an indignant Joel tells her, "Nurture your freaking body with sunshine! You don't need to do it with freaking chemicals!" In another, the boys get in trouble for throwing rocks at a rival school's bus, but they only did it out of an overdose of school spirit. When the principal brings them to her office for punishment, they try to impress her with their own homemade school anthem, whose lyrics begin, "Maynard High is the greatest freaking school, and we won't take no shit from nobody, and we won't ever stop being passionate!"
 
The relentless positivity is a very unexpected choice for an FX animated comedy — especially one that features abundant profanity, drug use, and jokes about animal sex (including a human character who has an unhealthy interest in Kangaroos) — and yet it's hard not to be charmed by Gary and Joel after a little while. They're idiots, but good-hearted idiots, and there are occasional moments where it seems like they're going to be able to steer the other characters — including overweight friend Darius (Romany Malco) and judgmental Megan (Kristen Bell), who only hangs out with them because no one else will have her — to good outcomes before things inevitably go awry.
 
And yet the actual comedy of the piece could use some fine-tuning. There are a number of strange supporting characters (including the aforementioned kanga-loving Australian neighbor, a Panamanian immigrant voiced by Fred Armisen and Sally Kellerman as the frustrated principal), but most of the laughs need to come out of what Gary and Joel are doing, and in these three episodes, the laughs are lacking.
 
By making Gary and Joel such fundamentally decent, if misguided, kids, the creators have set a much higher bar for themselves to clear than if they'd just made them sarcastic troublemakers who looked down on everything. I mentioned "Parks and Rec" before, which at the moment makes it look incredibly easy to generate comedy out of an incredibly nice, optimistic central character, but you have to remember that the first season of that show had all kinds of problems before they figured it out. In that case, I trusted the people in front of and behind the camera enough to stick around through the growing pains. Here, I'm a fan of "Always Sunny," and I like Gary and Joel enough at first blush that I'm going to give them a similar grace period. The toughest part of most new series is coming up with characters that the viewer will want to watch for weeks, if not years, on end, and they've already licked that part of it. We'll see if the rest follows.
 
Alan Sepinwall may be reached at sepinwall@hitfix.com