Training with future stars like Kristen Wiig and Maya Rudolph, Ms. McCarthy also met Mr. Falcone, who busted her in a Groundlings class for improvising a monologue she’d pretended to write on paper.  While her “Groundlings” classmates went off to “Saturday Night Live,” Ms. McCarthy became a supporting player on “Gilmore Girls,” as the embarrassment-prone Sookie St. James, and, in 2010, landed her lead role on “Mike & Molly.”  The following year, Paul Feig, the director of “Bridesmaids,” and its producer Judd Apatow were struggling to cast the character of a goofy friend to Ms. Wiig (who wrote the film with Annie Mumolo).  Mr. Feig said this character was written “to be very nervous and high strung, that friend who’s always falling apart, or at least just high maintenance.” But when Ms. McCarthy came in, wearing Guy Fieri-style bowling shirts and playing her rough and overconfident, Mr. Feig said, “It’s the funniest take on it I’ve ever seen.”  The success of “Bridesmaids” allowed Ms. McCarthy to write her own ticket: a male character in the comedy “Identity Thief” was made female so she could star in this film with Jason Bateman.  Then as she was wrapping “Identity Thief” in Atlanta last summer, Ms. McCarthy signed on for “The Heat” — barely two weeks before it started production in Boston, when it was called “Untitled Female Buddy Cop Movie” — knowing that Mr. Feig and Ms. Bullock had signed on.  “Identity Thief” became another box-office hit in February, but a particularly scathing review of the film drew national attention. Writing about the movie for The New York Observer, Rex Reed described Ms. McCarthy as “tractor-sized” and called her “a gimmick comedian who has devoted her short career to being obese and obnoxious with equal success.” Though this review was widely pilloried for its excessive cruelty, Ms. McCarthy did not immediately respond to it.  When Ms. McCarthy was asked about the review over lunch in April, her characteristically cheerful tone evaporated. In a softer voice, she said her initial reaction to reading it had been “Really?” and then, she said, “Why would someone O.K. that?”  Without mentioning the name of its author, Ms. McCarthy said: “I felt really bad for someone who is swimming in so much hate. I just thought, that’s someone who’s in a really bad spot, and I am in such a happy spot. I laugh my head off every day with my husband and my kids who are mooning me and singing me songs.”  Had this occurred when she was 20, Ms. McCarthy said, “it may have crushed me.” But now, as a mother raising two young daughters in “a strange epidemic of body image and body dysmorphia,” she said articles like that “just add to all those younger girls, that are not in a place in their life where they can say, ‘That doesn’t reflect on me.’ ”  “That makes it more true,” she said. “It means you don’t actually look good enough.”  Ms. McCarthy was about to say more when the restaurant began a long and very loud test of its fire alarm.  “I imagine that’s my publicist,” she said after a tension-breaking laugh. “The gods didn’t want us discussing this.”  For Ms. McCarthy, “The Heat” was, like “Bridesmaids,” an opportunity to build a character from the ground up, to give her frazzled, Patti Smith-style hair and an out-of-date wardrobe, and to get to shoot what she called “a crazy machine gun.”  For Ms. Bullock, who plays a strait-laced F.B.I. agent, it was important that “The Heat” be a movie where women played roles that could just as easily have gone to men, and could be a rare female-led film during the film industry’s period of peak testosterone.  “You don’t really see lady-times taking on the summer schedule,” she said.  But the greatest challenge they faced on “The Heat” was a ticking clock and what Ms. Bullock called the “Wild West mentality” of its hectic production.  “You didn’t have time to let any insecurity creep in,” said Ms. Bullock, an Oscar winner for “The Blind Side.” “The first day was like, ‘O.K., we’re not saying anything that’s on the page.’ Then we get into a slap fight.”  In these comic confrontations, Ms. Bullock said of Ms. McCarthy: “She will go for the jugular and, if you’re delicate about it, you’re going to sink. So you fire back — you go for the carotid artery.”  Mr. Feig said of Ms. McCarthy that it was “fun to watch her abuse America’s sweetheart,” but also to see how much more confident of a performer she’d become since “Bridesmaids.”  On that earlier film, Mr. Feig said, “she came in with all this inventiveness and creativity, but she was one of the players.” What she now shares with other movie stars, he said, is that they “know how to shine — they know what they want to do and don’t want to do, and they know how to take something that isn’t in their personality and do it better.”  Given the fickleness of the film industry, Ms. McCarthy said this could be her “only time to really pick things that I 100 percent connect with.” If her hot streak should fade, she said she was prepared. “I’ve been trying to play old-lady parts since I was in my 20s,” she said, “so I look forward to all of that.”  For now, Ms. McCarthy has enough clout to spend part of her summer break making “Tammy,” a comedy she wrote with Mr. Falcone and which he is directing, in which she plays an irresponsible woman on a road trip with her tough-as-nails grandmother (Susan Sarandon). Then she goes right onto another film, “St. Vincent De Van Nuys,” which pits her against Bill Murray, one of her comedy idols.  Ms. McCarthy previously got to work with another personal hero, Jane Curtin, who plays her mother in “The Heat,” and who, as a founding cast member of “Saturday Night Live,” taught her that female performers need not depend on others to create their material.  Watching Ms. Curtin with her “S.N.L.” co-stars, Ms. McCarthy realized, she said: “They’re the ones making it. They’re not just saying funny things — they’re actually funny.”  Ms. McCarthy tried to communicate something like this to Ms. Curtin on what she believed was their last day of filming together, but instead she unexpectedly burst into tears.  “I was like, get it together,” Ms. McCarthy recalled. “Don’t always be weird.”  Ms. Curtin then reminded Ms. McCarthy that she still had one more day of work.  “She was really nice about it,” Ms. McCarthy said. “But I was like, I can’t get out cool. I can’t do it.”  A version of this article appears in print on June 16, 2013, on page AR1 of the New York edition with the headline: McCarthy Goes Over The Top. Order Reprints| Today's Paper|Subscribe
Rising celebrity means she can have roles rewritten for her; and it has made her a target for unexpected and shockingly personal criticism.