L'ombre d'Emily

To accentuate the contrast between the scary and the funny, director Paul Feig made the decision to shoot the movie like a brightly-lit comedy. "Thrilling things happen in the daylight rather than in darkly lit rooms." He adds, "in the suburbs, there's not a lot of hiding among the white walls and bright windows."

When Stephanie receives the email about Emily being spotted in Michigan, you can see it is actually an email that has been typed but not sent. The shot of the computer screen shows the "Compose" tab of Stephanie's email is open (not the inbox), with the "send email" button at the bottom of the page.

In an alternate ending on the DVD, Sean assembles a flash mob that dances for Stephanie in the school playground, ending with Sean proposing to Stephanie.

Edited from A Simple Favor: Flash Mob (Alternate Ending) (2018)