One unexpected side effect of Peak TV in America has been the way lines between categories of TV shows have blurred to the point of being non-existent. Is "Orange Is the New Black" a comedy or a drama? What should we call "Transparent"? Is "Fargo" a series of miniseries, or not, because some characters recur in each season?

The only place this confusion really matters at all is come awards time, where the Emmys keep scrambling to make sense of things. But the trend reflects a desire to make shows that reflect a distinct creative vision, categories be damned. If Louis C.K. wants to tell fart jokes on "Louie" one week, he can, and if he thinks the story needs to be darker and more introspective the next, great.

The one type of show that has stayed largely immune from that confusion is the traditional multi-camera sitcom. A "Big Bang Theory" or an "Undateable" might occasionally reach for a more poignant moment, but for the most part, multi-cams remain comfortable as joke delivery systems where you know what you're going to get from week to week, and even scene to scene.

But then there's "Mom," which begins its third season tonight at 9 on CBS. Created by Chuck Lorre, Eddie Gorodetsky, and Gemma Baker, it remains a throwback to '70s and '80s comedies like "All in the Family," "Taxi," and even "Cheers," which took their characters seriously enough to be comfortable with purely dramatic scenes, which in turn only makes the laughter feel more potent.

The show's main characters, single Christy (Anna Farris) and her own mother Bonnie (Allison Janney), are both recovering addicts, perpetuating a cycle of setting bad examples to their children. Last season, the family was briefly homeless, Christy's father died while having sex with Bonnie, and Bonnie fell off the wagon when a back injury forced her to take pain medication. The show doesn't flinch from the complicated emotional realities of its characters' lives — the heavy stuff is likely what's won Janney two Emmys so far for the role — and has no qualms about doing long dramatic scenes that leave the studio audience silent(*) as Christy, Bonnie, and their loved ones grapple with mistakes in the past and present, as well as ones they fear they'll keep making in the future.

(*) That's one notable change from the '70s. Go back and watch some of those heavier episodes of "All in the Family" or "Taxi," and you can hear the studio audience laughing wildly at anything even vaguely resembling a joke, because they understandably expected to be having a fun time. Other sitcoms (particularly ABC's TGIF shows in the '80s and '90s) would occasionally drop the jokes in favor of shameless sentimentality designed to elicit loud "Awwwwww"s; this is much quieter and more genuine than that.

The third season premiere expands the generational approach with the introduction of Ellen Burstyn as the mother Bonnie hasn't seen since she was very little. Burstyn has plenty of experience at comedy, and Janney's great at it, but when the two women are together(**), there's a lot of pain to deal with first, and the jokes are comfortably nudged to the corners of the episode. It's smart, and honest, and doesn't try to oversimplify the situation for the sake of getting in and out of it in 20-odd minutes of TV.

(**) For a few moments, the show has Oscar winner Burstyn, Emmy winner Janney, and Oscar nominee June Squibb all interacting, which is not too shabby. And Squibb is very funny.

Next week's episode (the second of two that CBS made available to critics) is more straightforwardly comedic, with Christy dealing with an uncomfortable new situation at work, and a lot of banter among the women at the regular AA meeting (Jaime Pressly and Beth Hall are now cast regulars, following last season's similar promotion of Mimi Kennedy). But the emotional grounding the show gets from the more dramatic material gives the comedy more richness. When Christy considers quitting her job, it's a much more fraught situation than it would be if she didn't so desperately need the stability and structure it provides. It works the other way, too: when Bonnie and Christy play host to a recovering young addict (Emily Osment) with no place else to go, the sadness of the situation gets leavened a bit — without ever being cheapened — by Bonnie's understandable fear that the girl might steal their stuff and sell it to buy more drugs.

These days, it's not the least bit surprising when single-camera comedies take a turn for the dramatic (like the clinical depression arc this season on "You're the Worst"). It would be very easy for the remaining producers of multi-cam to leave that stuff to their more fashionable counterparts and just stick to telling jokes. "Mom," thankfully, is a strong reminder of just how elastic this 64-year-old format is.

Alan Sepinwall may be reached at

Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "TV (The Book)" about the 100 greatest shows of all time, is available now. He can be reached at