Bullock stars as Sarah Ashburn, an FBI agent hoping for a promotion and high-tails it from her home base in New York City to Boston, to help solve the mystery behind several murders. Standing in Ashburn’s way is a hard-hitting Boston police officer, Shannon Mullins played by Melissa McCarthy, who’s not happy that the FBI – especially the stuck-up Ashburn — is treading on her turf. Ashburn is determined to wrestle the case away from Mullins, but the disheveled, foul-mouthed, in-your-face cop is a formidable adversary. They’ll soon discover they have more in common than they ever thought possible, including their misfit status and complementary skillsets.
“Ashburn’s effectiveness as an FBI agent comes from her meticulousness, stubbornness and thoroughness,” says Bullock. “But she’s completely inept when it comes to any kind of social interaction. She’s trying so hard to make up for that particular weakness that she becomes insufferably arrogant on the job. Ashburn is respected but not liked because she isn’t a team player. Every time she opens her mouth, people cringe.”
The improvisational nature fueled the fun and on- and off-screen bonding. “It is great working with Melissa,” enthuses Bullock. “She comes through the door and improv is the way that she does things. Then we had a director who comes from that world too and nearly everyone in the cast was also from that world. The world of comedy that I had been familiar with was always very controlled. There was the script and you had to go through 27 people and the studio before you could change a line. I always wanted to do this kind of comedy that we have in THE HEAT (which I have done in real life, sort of free form,) but I was never really allowed to experience what it was like before on a film.
Walking onto the set of THE HEAT it took me a couple of days to realize: ‘I’m allowed to do it.’ It was very liberating. When you are around that, you take it in and you want to improve your game. It is a muscle that you have to exercise and if you haven’t had much time exercising that muscle, it gets stale. Watching these people work is exciting and inspiring, but daunting sometimes too.”
“Melissa has great moves,” says Bullock,”discussing McCarthy’s comedic skills. “When I saw her dance, I knew we were going to be fast friends.We did the dancing with no practice 
“We said: ‘let’s not rehearse anything,’ ”interjects her co-star. “Let’s just be as terrible as we’re capable of being. Poor Paul turns around and we both have our faces taped,” laughs McCarthy, “and he’s like, ‘What’s happening?’ It was a weird descent into controlled madness. It was really fun. There was a lot of ruined tape,” she says. McCarthy adds: “Yeah, I got the moves, but I don’t have the sense to stop whatever’s going on.”
“We really hit it off, she is like my sister,’’ adds Bullock. “I’d say it’s rare that actors get together and have the kind of chemistry and connection we have together. It somehow just works and it’s something inexplicable that is bigger than what is on the page.”
“The Heat” opens June 27 in theaters from 20th Century Fox to be distributed by Warner Bros.