It wasn’t the explosive action sequences, the shout-out to Blockbuster Video, or even the old lady getting punched in the face that resonated with some viewers of the new Captain Marvel trailer.

It was that star Brie Larson isn’t shown smiling much.

The Marvel Studios movie trailer, which has racked up more than 36 million views in less than a week, led some social media users to Photoshop a smile onto the actress’ face. In response, other users posted images of Marvel men not bearing their teeth. Others countered with their own Photoshop wizardry, upturning the mouths of Thor, Iron Man, Captain America and Doctor Strange.

Larson, who won an Oscar for Room in 2016, posted those images without comment in a series of expired Instagram "story" posts. The call for her superhero to “smile more” echoes what some women have called a form of sexist harassment that implies a woman’s expression should be controlled for the pleasure of men. The outrage spawned the social media hashtag “#selfiesforbrie” in which mostly women and young girls shared pictures of themselves sporting a variety of facial expressions.

“About time Marvel gives us a solo female superhero lead with an actress that fights for what’s right on and off screen,” wrote one user. “Be a HERo with or without a smile.”

The actress hasn’t commented explicitly about the outrage, but wrote about the #selfiesforbrie hashtag on Twitter last week.

“I loved seeing all your expressions. Moody or smiling or coy or fierce or whatever is YOU," she wrote. “Thank you. It was truly a highlight of these few wild days.”