Rachel Bloom as Rebecca Bunch. Photo: Robert Voets/The CW

Crazy Ex-Girlfriend, which starts its fourth season Friday night on the CW, is one of those shows that looked on paper like it couldn’t go the distance until it did: a combination romantic-comedy, workplace satire, and musical fantasy about a lawyer named Rebecca Bunch (co-creator and star Rachel Bloom) who moves from New York to West Covina, California, to stalk a teenage crush (Vincent Rodriguez III’s oblivious hunk Josh Chan). At times suggesting an unholy fusion of an anything-goes musical telenovela like Glee or Cop Rock and an anti-hero drama built around a charismatic screw-up, the series is mesmerizing in part because it continues to exist and try new things despite being out there all by its lonesome. The closest thing to it is another CW series, Jane the Virgin, which has its own aesthetic but likewise rides the line between drop-dead serious and just joking. Chimeras like CXG, as it became known, rarely get onto commercial TV in the first place, and if they do, they don’t always know how to sustain their concept over the long haul.

Bloom and co-creator Aline Brosh McKenna’s series has already beaten the odds, digging progressively deeper into its heroine’s psyche and continuing to deliver consistently clever, sometimes dazzling musical numbers (all of them original, though they’ll sometimes reprise an audience favorite with new verses or a different take). Over the years, CXG has also built out a deep bench of supporting players, which includes Donna Lynne Champlin as Rebecca’s best bud, Paula Proctor, who increasingly seems like her true soul mate; and Pete Gardner as her boss Darryl Whitefeather, who came out as bisexual and is now the father to a child made from Rebecca’s donated egg and carried by Rebecca’s roommate Heather Davis (Vella Lovell). The fourth season picks up with Rebecca about to enter county lockup after pleading guilty to pushing her own stalker, Trent Maddock (Paul Welsh), off a balcony to prevent him from killing her lover and boss Nathaniel Plimpton III (Scott Michael Foster). Rebecca’s attack broke every bone in Trent’s body (for the second time!), made her a tabloid celebrity, put her on trial for attempted murder, and led to her pleading guilty — or as she kept saying, “responsible,” a word she’s never really embraced up till now.

That Rebecca would embrace a stint in jail as a form of atonement seems to indicate emotional growth. But as other characters point out to her, it’s really a performative, narcissistic substitute for truly making amends and trying even harder to understand her “privileged, myopic” (her words) mind-set and rewire her brain so that these sorts of incidents can’t happen again. “It wasn’t really a plea,” the judge tells her. “It was more of a speech, filled with irrelevant details that you delivered to this lady — [indicating Paula] — with your back to me.” “I need to do penance,” Rebecca insists, “if not for this crime, then for all of my past crimes, both real and metaphorical.”

Will she ever break through the walls preventing her from real self-knowledge and lasting change? The titles of season four’s episodes offer some hope: They depart from the established template, which always worked in the names of her love interests (“Josh Is Irrelevant,” “Nathaniel Needs My Help”), and instead center Rebecca (“I Want to Be Here,” “I Am Ashamed,” “I Am on My Own Path”). But it would be unwise to get too complacent about expecting the show to take a sunny, upbeat turn. Those hopeful phrases could seem menacing if uttered by a scary person, and Rebecca, for all her wit and self-deprecation, can be terrifying.

As is often the case on CXG, other major characters manifest their own version of Rebecca’s problems — in this case Josh and Nathaniel, who share the premiere’s second musical number, an all-timer that builds into an 11-part ensemble piece that deploys split screen and meta lyrics to impressive effect. Nathaniel and Rebecca’s stories are mirrored through the idea of self-punishment without insight: Nathaniel, who was sleeping with her last season despite having a girlfriend, pays to join a camping service that abducts you, beats you within an inch of your life, then dumps you in the woods with a spoiled sandwich and a canteen full of sand. The name of this service could be an alternate title for CXG: “Death Wish Adventures.” If that doesn’t turn out to be the title of an upcoming musical number, I’ll eat Nathaniel’s sandwich.