Looking back, Bloom thinks that her classmates were picking up on something that no one else, including her, recognized at the time, which was that she was dealing with some fairly significant mental-health problems. “I had pretty severe anxiety and depression and what I think was O.C.D.,” she said. “I had looping compulsive thoughts based around sexual shame — by the way, that didn’t come from my parents. If anything, they erred on the side of being superopen about sex. But it was like, any sexual thought, I’d have looping thoughts about what that meant. It was sex shame, body shame, dirt shame.” Bloom still suffers from bouts of anxiety.

The show takes the concept of craziness and examines it with episodes of both farce (Rebecca Bunch, high, trying to break into her shrink’s home via a doggy door) and utter seriousness. Rebecca’s West Covina law-firm boss tells her, when she melts down in a meeting, to come back Monday as “the happy Rebecca that we all know and love.” “Such a good tip,” she responds. “ ‘Be happy.’ ”

By the time Bloom got to high school, the worst of her O.C.D. had passed, she thinks, and her talent as a performer was also gaining respect from her fellow students. But as Daniel Green, a close friend Bloom has known since they dated in high school, put it, “Do you ever really shed your middle-school persona?” Green, who is now an internist, was on set that day at the apartment complex, visiting Bloom and watching her shoot. By the time he started dating her in 11th grade, people were still commenting on the red, glittery Dorothy-in-Oz slippers she wore every day for close to a year in elementary school. “People were always saying, ‘I can’t believe how talented she is — she was so weird!’ ” Green said. “That was always the second half of the sentence.”

As a makeup artist applied gloss to Bloom’s lips on the set, Bloom turned to Green and asked, “What does the inside of a body smell like?” “Not much,” he answered. Bloom thought for a moment, then asked, “When you look at Jennifer Lawrence, do you see a pretty girl, or just a walking sack of guts?”

To Green, the character Bloom was playing — a bright, high-functioning professional with an ingenuous, unedited oddness — is not that different from the person she was in high school, and still is, so far as he could tell. “I don’t think she lies to herself quite as much as Rebecca does,” he said. “She might amp the volume up, but she’s the same person.”

Perhaps a childhood like Bloom’s can produce an unusually bold person. So what if someone doesn’t like her act, or thinks she’s vulgar, gross or weird for imagining someone sexually fantasizing about Ray Bradbury? What’s the worst that could happen — someone might mock her? She has been through that before. Or perhaps Bloom was always fearless; maybe there was a rawness, or an otherness, to her as a young child that her peers could not then tolerate, but that adults, who eventually come into their own sense of mortality and misery, now enjoy watching her explore through her show. Whatever the reason, Bloom is invariably described as brave by her friends and colleagues, both in her curiosity and in her creativity. “Sometimes I get to improvise with her,” Pete Gardner, who plays her boss, says. “And I love doing it. Because when I look into her eyes, I see no fear.”

By the end of the day, Bloom was shooting some final scenes of the “Cold Showers” song at an outdoor pool at the apartment complex. She was supposed to swan dive off the side of the pool onto a small raft that would drift a foot or two in the water in front of a line of dancers on the edge of the pool. The light was fading, and there was some back and forth about what would happen if Bloom missed the raft. The director wanted her to weigh in on where to position the camera. She thought about it, with dozens of people waiting on her call. A chill was already in the air. Bloom had her face in her hands as she tried to concentrate. “Let’s do it proscenium-style,” she finally said. “I can be on the float and be facing them on my stomach.” A crew member called out, “Let’s just go, we gotta go!”

The chorus, an assortment of the show’s regulars and others cast to play Josh’s neighbors, was singing words about crack and cold water that made no sense (even though the lyrics also include the line, “This makes sense!”). Then Bloom belted: “Gasp with an uppercase G, that ends with P, the first letter in ‘pool.’ ” At that point, she threw her hands in the air and dove, Superman-style. Bloom landed squarely on the raft, sailing into the middle of the pool. She could just as easily have missed, flailing in front of all those people and getting soaking wet, her pale blue silk shirt transparent. She had already considered that possibility. “It’ll be funny,” she said. “It might even be better.”