Dunst had been doing several takes of a scene where her character smokes pot. She hadn't eaten much that day, and she went back to her room to rest. That's when she started to feel like "I was losing my mind." She began pacing and called her director to tell her that she needed to go to the hospital.
"I'm shaking. I'm hot. I'm just flipping out," the Spider-Man actress said.
One of Dunst's producers came to check on her and investigated her pot props. That's when he told her the news: "'Oh, you smoked a full blunt on one of the takes,'" Dunst said, recalling her producer's words.
"And we're talking about Humboldt weed, OK?" Dunst continued. "I don't smoke full joints. This is like strong sh-it."
When Kimmel asked how the real pot got there, Dunst said, "Well, they had locals roll the joints for us, and they just threw some in for fun."
"I was like crying, laughing, eating a peanut butter sandwich," she later continued. "I couldn't film anymore. They sent me home. I was a total mess. I've never been that stoned in my entire life."
Watch the video to see Dunst tell the whole story.