Sometimes you need musical legend Josh Groban to reveal some harsh, hard-to-hear truths about life ... like how you should never "bang your ex-boyfriend's dad." While that may seem obvious, it's clearly a lesson that Crazy Ex-Girlfriend's Rebecca Bunch (Rachel Bloom) needed to learn, because that's exactly what she did in the pivotal, heartbreaking hour that was "Josh's Ex-Girlfriend Is Crazy." After everyone in Rebecca's life discovered the truth about her past — attempted arson charge and mental-hospital stay included — the self-described heroine of her own musical tried to literally run away from her problems with Nathaniel (Scott Michael Foster), only to be stopped by her friend Paula's ill-timed intervention.

Surrounded by friends and co-workers and unable to escape the truth any longer, Rebecca projected all her insecurities onto her friends, pushing them away by saying the meanest things possible to each one. And after her desperate attempts to terrify Josh (Vincent Rodriguez III) failed to get him to finally acknowledge her and explain why he left her at the altar, she was ready to hit rock bottom. What finally pushed her there was an unfortunately timed butt dial from none other than her ex Greg while Rebecca was frequenting his old bar haunt. His dad Marco (Robin Thomas) was also there, and proudly told Rebecca that Greg was really happy, sober, and had fallen in love with someone else. Not exactly what she wanted to hear about an ex when she was at her lowest point. So alcohol plus a much-needed compliment from Marco equaled sex with her ex-boyfriend's dad. Rebecca, meet rock bottom.

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But Crazy Ex-Girlfriend creator and executive producer Aline Brosh McKenna reveals that what shook Rebecca to her core wasn't the act itself, but the epiphany that she's not at the center of a story. Because Rebecca is "very self-aware," she's been searching for a story to tell herself about her life, and now she's finally realizing that life doesn't fit neatly into story arcs.

"One of the reasons that this show is a musical is because she's grasping for a narrative to cloak herself in," McKenna says. "She thinks a story or type of character will insulate her from her pain. She grabs at being the ingénue in the first season and being the smitten girl in the second season, before grabbing the woman scorned. She's grabbing at all these received scripts about female behavior and in this episode, she finally runs out of stories."

And "that's literally what the Josh Groban song is about," according to McKenna. As Rebecca walked home alone after making her latest mistake, Josh Groban's voice could be heard singing to her about how "life doesn't make narrative sense." Then the camera suddenly panned back to show him walking next to her, belting out the lyrics at her about the truth she's finally realized.

"She's out of stories to tell herself," McKenna continues. "The fiction she created when she saw Josh Chan on the street [in the series premiere], that's over. The question for Rebecca is, can she find a more authentic story that comes from inside of her and isn't a received narrative from the outside, from culture?"

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For the first time, a song is actually from the point of view of the show singing to Rebecca, and not the other way around.

"It's at the point where she thinks the world has abandoned her, and when we first started talking about the song and what it could be, I got teary talking to the team about creating a song that shows our compassion for her," McKenna says. "When she thinks she's lost, having him sing that song tells her the story is not over, we're still here and we're still cradling Rebecca Bunch in our hands. I actually wept at the meeting where we talked about it, which is not a thing I do a ton."

McKenna laughs as she remembers that emotional moment in the writers room, and it's clear how much she means it when she says, "We love Rebecca."

"Rachel and I feel almost a maternal feeling towards her and it's the show's sense of putting her under our wing and saying, 'You may not know it, but there is someone here guiding you and protecting you,'" McKenna says. With the idea of having a celebrity on the street telling Rebecca that things will be okay coming first, the lyrics then came about from an offhand comment McKenna made to Bloom and songwriting team Jack Dolgen and Adam Schlesinger during a brainstorming session. As for how they got Josh Groban, "it was a rare instance where we wanted someone like Josh Groban and we ended up actually getting Josh Groban," McKenna says.

After Bloom met the singer at the Tonys and found out he was a fan of the show, the stars aligned and he miraculously ended up being available to shoot the climactic scene where he played himself.

"The shot where Josh appears is one of my favorite shots of the entire series as you realize, 'Holy shit, that is Josh Groban!'" McKenna says with a laugh. "[Director] Joseph [Kahn] designed that shot and that's the only way he shot that. I was like, 'This guy's a baller. Man, I hope it works.' And it worked perfectly."

In fact, McKenna credits Kahn with achieving the massively complicated tone for the episode. "Getting the tonal shift down was the biggest challenge," she says. "We knew we needed a really special director for it and Joseph hasn't done a lot of episodic television but I knew his work and how talented he was and I just had a feeling that he would be perfect for it. He can capture that intensity of a thriller while maintaining the comedy, and it's really darkly funny."

While the hour was hard to watch as a viewer, it needed to be to show the truth of what Rebecca was thinking and feeling and how far she's come to get to this point. "We didn't set out to make people uncomfortable. It felt like we were finally mining this thing that had been there all along," McKenna says. "It was like a zit we had been waiting to pop. It's a very intense episode. It's really digging into the premise of the series and pushing it."

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Though Crazy Ex-Girlfriend has certainly never held back with its storytelling, especially in terms of Rebecca's mental health issues, McKenna feels they've always had their "kid gloves on" because Rebecca started out "being much more conventionally 'likable.'"

"It felt like an exhilarating leap to finally dig into what she's been restraining herself from doing," McKenna says. "Even though there's obviously a darkness and a sadness to it, there's also a sense of relief that she has that we had. Our goal always was to get inside her head and see what leads someone to this extreme place and this is now 35 episodes in, we know her and understand and love her."

McKenna is quick to say they don't justify or endorse any of Rebecca's behavior, "but Josh really has been a coward and was avoiding her and that only reinforces this sense of abandonment that she feels from him."

"These movies, especially these revenge stories, work because there's a sense of catharsis and a sense of relief," she says. "She's finally getting to express the most extreme edges of her behavior and we're with her all the way. It's really about getting behind the eyes of someone who is experiencing this."

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It's an easily relatable story of rejection pushing someone to seek revenge, even though it's always a futile reaction. "You want to recreate the pain in them that's inside of you," McKenna says. "The illogicality of revenge is that you want to make someone feel awful, but to what end? It never makes you feel better."

As a show whose Season-1 theme song was careful to quip that "the situation is a lot more nuanced than that," Crazy Ex-Girlfriend's showrunners wanted to wait long enough for the audience to really learn to love Rebecca as a person and see and know her behavior first before she would come to literally embody the show's eponymous trope. They also didn't want to stigmatize or stereotype someone who gets to this place, which is one of "real desperation."

"At the end of this episode she's going home [to New York] because she feels like she's ruined all of her relationships," McKenna says of where Rebecca goes from here. "They will then have to deal with her absence. It changes everything."

Viewers know that "home" is not a happy place for Rebecca. "But she really has nowhere else to go and Paula doesn't know what else to do except deliver her to the person who is her actual mother and just hope for the best," McKenna says. "The story progresses so it isn't any one thing. That's why the theme of the show this year is not a musical about revenge, it's about more broadly her journey from here. It takes a number of forms going forward."

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As for finally getting closure on Greg after former series regular Santino Fontana shockingly exited the series in the middle of last season, McKenna reveals they never discussed having him actually show up in this episode. It was always just going to be the idea of Greg, her last resort, finding happiness that pushed Rebecca over the edge.

"She was dreading that he got a happy ending in the way that some part of you always hopes your exes are not doing that great," McKenna says. "So it turns out that he actually is doing great and since she tends to be paranoid, she thinks it's about her. Everyone gets to be happy except her so she takes it personally as she often does."

And apparently Rebecca sleeping with Marco was something Bloom has been joking about for a long time – "ever since that character first appeared on the show," McKenna says, because of the "banter-y relationship" they had when Rebecca dated Greg.

"She's grasping for some something that will make sense, another story she can inhabit in some way," McKenna says of that ultimate mistake. "He shows her warmth and says something nice to her in a moment when she's feeling really shitty about herself, so it seemed like the perfect way for her to find her bottom."

But if rock bottom looks and sounds like Josh Groban, it can't be all bad ... (or at least that's the narrative we're telling ourselves).