There have been countless characters who have wormed their way into TV viewers' hearts, from ruthless antiheroes to complicated women, dysfunctional man-children to flawed superheroes. But of late, there's been a new breed of fictional figure, one that struggles with mental health issues and deals with them with a blend of humor and pathos. And two of the most relatable of these characters happen to be a talking horse and a talking dog.

We're speaking, of course, about BoJack Horseman (voiced by Will Arnett), the titular character in Netflix's dark comedy about a washed-up '90s sitcom star — who happens to be a horse — whose depression propels him into a cyclone of self-destructive choices; and Martin the dog (voiced by Samm Hodges), the narrator and star of ABC's new critical darling Downward Dog, who anchors every episode with an existential crisis about his relationship to his owner/"life partner" Nan (Allison Tolman).

BoJack and Martin are certainly not the first such characters who have struck a chord with viewers. The long history of anthropomorphic animals can be traced from Mr. Ed and Bugs Bunny to Family Guy's Brian Griffin. But none of their predecessors have addressed issues such as depression and anxiety so explicitly. And while such topics are sometimes seen as "too heavy" when they're embodied by human characters, depicting the struggle through animals somehow evokes more empathy (at least, with this human viewer).

In the case of BoJack Horseman, which is currently prepping its fourth season, viewers quickly realized that the show is so much more than a silly cartoon featuring talking animals and excellent puns. It also offers an incredibly accurate and gut-wrenching depiction of the paralyzing and ruinous effects of chronic depression. BoJack is one of the darkest — if not the darkest — show on television, and BoJack the character may as well have had Walter White as a life coach.

BoJack Horseman and the infinite sadness

Downward Dog, on the other hand, brilliantly attempts to answer the age-old question, "What are our pets really thinking?" As voiced by Hodges, who co-created the show and has spoken openly about overcoming a stutter that he developed in childhood, Martin offers his endearingly naïve perspective about the minutiae of everyday human life, whether it's believing he's developed superpowers after Nan buys him a magnetic collar to control his dog door, or resenting Nan and her prudishness for forcing him to suppress his deep desire to eat trash.

So what makes the two characters so relatable? While not every viewer will identify with BoJack, it's impossible not to sympathize with him on some level — even if you're simultaneously appalled by his actions. Credit for this goes mostly to Arnett's skillful line readings, but also the writers' unwillingness to let BoJack become completely irredeemable. Each time he hits a new low in his actions, he hates himself as much as the people around him do.

With Martin, there's an added aww factor since the character is a real-life, non-animated canine — a former shelter dog named Ned. But the biggest part of Downward Dog's charm is how Martin's struggles mirror Nan's, and vice-versa. When Nan goes on a rebound "double date," Martin in tow, with a snobby dog owner and his refined pet, it doesn't take long for both her and Martin to realize they're aiming way out of their leagues.

And while Martin ponders questions like whether he's a narcissist and has anxious dreams about the cat next door, Nan's fretting about whether her on-again, off-again boyfriend (Lucas Neff) is marriage material, and trying to make a name for herself at work. Despite his and Nan's ups and downs, Martin concludes every episode with the realization that he and his owner not only love each other, but truly need each other. That's a sentiment all viewers have felt, whether for a pet, or another human.

It's interesting to wonder whether Martin or BoJack would be as likable and empathetic if they were humans. The answer is no. It's in our nature as humans to project a sense of innocence and vulnerability onto animals, especially commonly domesticated ones like dogs and horses. Whereas human characters — even the "good" ones — are all inherently flawed, the same can not be said for most animals.

Particularly in Martin's case, he'd be pretty difficult to stomach as a human being. But the fact that he is a dog is, after all, the point of the show. If Martin were a middle-aged man instead of a 7-year-old mutt, he'd probably be viewed as an ignorant stage-5 clinger who's completely detached from reality — unappealing qualities in men and women, but par for the course when it comes to our four-legged friends. But Downward Dog works because Martin's anxieties feel utterly relatable in modern times; whether he's worried about Nan spending too much time at her job, or patting himself on the back for sticking by Nan while she's been on an emotional rollercoaster with the same guy for six years.

On BoJack, the fact that the title character himself (and most of the other characters) are animals is a key element of the show's absurdist brand of comedy. After a while, it's easy to forget that BoJack is a horse at all, probably because he walks around on two legs and otherwise behaves like a human.

For decades, talking animals have been a cute conceit by which to lure in viewers of all ages. But the creators of BoJack Horseman and Downward Dog are going further, and cleverly using their protagonists as (pardon the expression) Trojan horses to explore darker issues that, on the surface, might turn viewers off. When it comes down to it, Martin and BoJack are two of the most human characters on television.

Seasons 1-3 of BoJack Horseman are available to stream on Netflix. Downward Dog airs Tuesdays at 8/7c on ABC.