In one scene, she discussed auditioning for the breakout role, and the footage cut to what appeared to be a throwback photo of her as a little girl.
However, one fan pointed out that it was not, in fact, Watson in the photo of the little girl with Minnie Mouse ears, but rather actress Emma Roberts. Roberts, 30, had posted the throwback photo to her own Instagram account all the way back in 2012.
On Wednesday, Watson posted the same pic to her own account, jokingly writing, "I was NOT this cute, @emmaroberts 😂 #emmasistersforever."
"Well spotted Harry Potter fans! You brought an editing mistake of a mislabeled photograph to our attention. New version up shortly," the producers said in a statement to Entertainment Weekly earlier this week.
This wasn't the only mistake the special made. Real-life twin brothers James and Oliver Phelps, who appeared in the reunion, were mislabeled during one of their interview scenes, which Oliver, who played George Weasley to James' Fred Weasley, pointed out on Instagram.
"↔️ I guess after all those pranks over the years somebody decided to get their revenge," Oliver wrote on Instagram. "It was fantastic to be part of the HP reunion. Hope you all enjoyed it. #ReturnToHogwarts."