Gyllenhaal shared a black-and-white throwback photo -- which appears to be from a yearbook -- of himself donning a pair of dark, round eyeglasses.
"I’ve worn my glasses ever since I parted my hair meticulously with gel (see above), which is why NEW EYES has always been near and dear to my heart. Since 1932, @neweyes_ has provided eyeglasses to people who needed them most," he wrote in the caption of the post.
The star continued: "I’m thrilled that they’ve partnered with @theinspireprojectus to create Project Human: Changing the Way We See the World, a speaker series coming to schools and remote learners this fall. Project Human is designed to spark conversations focusing on unity and equality. It’s an opportunity for students to interact with public figures and do what they do best: Keep ‘em on their toes!"
While Gyllenhaal's mind may be on the project, his followers were thinking about something else entirely: Swift's song "All Too Well."
Swift, 30, is rumored to have written the song, included on the album "Red," about the actor.
"'You used to be a little kid with glasses in a twin sized bed,'" quoted one fan in the comments in reference to a lyric from the song.
"TS was right," said another, again adding the lyrics.
"All i hear is all too well when i look at this," said another fan.
At the time of publication, the post had received over 743,000 likes and more than 6,000 comments.
YouTube sensation Rachel Zegler poked fun at the actor in the comments.
"I'll be honest mate you set yourself up for this one," the actress joked.
Another famous lyric from the song references a scarf that Swift may have left at the home of Gyllenhaal's sister, Maggie Gyllenhaal.
Also an actress, Maggie addressed the song back in 2017 during an episode of "Watch What Happens Live."
"I never understood why everybody asked me about this scarf, what is this?" she asked.
After host Andy Cohen explained the reference, Maggie said she's "in the dark about the scarf."
"It's totally possible [she left a scarf at my house], I don't know," she said. "I have been asked this before and I've been like, 'What are you talking about?'"