Aline Brosh McKenna, the co-creator (with star Rachel Bloom) of the CW’s “Crazy Ex-Girlfriend,” is hard at work on the third season of the musical comedy, after the season-two finale saw Bloom’s Rebecca Bunch left at the altar by her longtime obsession, Josh.

What can you reveal about the new season of the show?

The third season is in some ways the promise of the series — it’s more what you might imagine when you hear the title. She’s gotten to the point where she’s exhausted the gentler options of getting his attention.

What was the biggest challenge of the previous season?

We had a big change in terms of writing off a character and adding a new character. We spend a lot of time, effort, energy and craft doing that in a seamless way. Especially introducing Nathaniel (Scott Michael Foster) in a way where it’s very clear what trope we’re sending up with him. Our show revolves around rom-com tropes. Josh was the idealized high school quarterback; Greg is the overlooked nice guy. Nathaniel harkens back more to those James Spader rich asshole characters.

There’s a fan theory that the show is taking place in Rebecca’s head.

People have asked me that. I can completely dispel that theory. The musical numbers take place in her head, but the show takes place in the real world.

What’s your favorite song from the show so far?

I don’t have a favorite, but last year Paula [Donna Lynne Champlin] and Rebecca sang “You Go First,” which is one I relate to because it’s an ’80s ballad — that’s when I was in high school and college. I tend to gravitate toward the Paula songs, as we’re closer in age.

Have you thought about doing a cameo on the show?

No, I’m pretty bad. I really sing out of tune.

Things you didn’t know about Aline Brosh McKenna

Age: 49 Birthplace: France Raised in: New Jersey Other works: “The Devil Wears Prada,” “27 Dresses” MUSICAL BACKGROUND: Was in “Gypsy” in high school