"Thank you mom for digging these pics of @taylorswift and I harmonizing like buttah on summer nights twenty five years ago out of storage," the actor captioned his Thursday, February 1, Instagram post from "June 2000."
"Also trav the note is an f-sharp if you're interested," Mitnick, 36, added, referring to the blonde beauty's boyfriend, Travis Kelce.
The photos showed Mitnick dressed in a black leather jacket and T-shirt, while Swift donned white in the first two pics. In the third shot, the Grammy winner, 34, rocked voluminous curly hair and a black outfit just like Olivia Newton-John did at the end of the 1978 film.
Fans went nuts over the throwback pictures, with one person commenting, "This just further proves that Taylor had always been THAT girl…I can see why she is ruling major stages across the globe."
"WHY HAVE YOU BEEN HIDING THIS GOLDEN NUGGET OF INFORMATION FROM US?!?!" one Swiftie asked, while another wrote, "Baby TayTay 🤧💜😭."
Mitnick said he's mentioned the photos before, joking, "I’m sorry why did this not get this kind of attention in like March when I told you all about it in a shameless attempt to goose my book sales."
The "Cruel Summer" crooner is currently gearing up for the next leg of her tour, which kicks off on Wednesday, February 7, in Tokyo, Japan. Though she's playing several more shows in the city, rumor has it that she'll be returning to the U.S. to catch her boyfriend, also 34, play in the Super Bowl on Sunday, February 11.
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If Swift does show up for the big game in Las Vegas, it will mark her 13th time attending a Kansas City Chiefs game this NFL season.
Some football fans have grown tired of seeing the guitarist on the TV when she's there to cheer on her man, but the music icon has brushed off the drama.
"I don't know how they know what suite I’m in," she shared in her interview with TIME. "There’s a camera, like, a half-mile away, and you don’t know where it is, and you have no idea when the camera is putting you in the broadcast, so I don’t know if I’m being shown 17 times or once."
"I’m just there to support Travis," she explained. "I have no awareness of if I’m being shown too much and pissing off a few dads, Brads and Chads."