According to Moviefone’s Sharon Knolle (which is to say an Entertainment Weekly interview that she’s quoting), Brad Pitt agreed to do Se7en only if the ending with Gwynneth Paltrow‘s head in the box would definitely be stuck to, and if his Detective Mills character would absolutely shoot Kevin Spacey in revenge.
“I will do it on one condition: The head stays in the box,” Pitt told Knolle. “Put in the contract that the head stays in the box. And he’s got to shoot the killer in the end. He doesn’t do the ‘right’ thing, he does the thing of passion.”
But iffy test screening reactions led to “some execs” getting cold feet. “They go, ‘You know, he would be much more heroic if he didn’t shoot John Doe,” Pitt recalled. “And it’s too unsettling with the head in the box. We think maybe if it was the dog’s head in the box…'”
Se7en was a New Line release, so the execs who mostly likely suggested a dog’s head instead of Paltrow’s were….? If I had to guess I’d say it was probably former New Line toppers Bob Shaye or Michael Lynne. Or perhaps exec producers Arnold and Anne Kopelson.