• The cast of "Harry Potter" reunited in the new HBO Max special, "Harry Potter 20th Anniversary: Return to Hogwarts"
  • An eagle-eyed fan noticed that a throwback photo of Emma Roberts was shown in the special instead of Emma Watson
  • Producers admitted they had used the wrong photo and promised to correct the mistake

HBO Max accidentally used a photo of Emma Roberts instead of Emma Watson in the new special, "Harry Potter 20th Anniversary: Return to Hogwarts."

In the reunion special, which started streaming Saturday, Watson, who played Hermione Granger, discussed her childhood memories of the "Harry Potter" franchise. However, as the 31-year-old actress was speaking, a photo of Roberts, 30, was shown on screen.

"I think I probably would've been about 8 years old. I think that's probably when the first one came out. It became, like, our family thing," Watson said of the "Harry Potter" books. "My dad used to do all the voices, and my brother and I just became obsessed. We would just beg him to keep going."

One eagle-eyed fan noticed the mistake and posted about it on Twitter.

"Guys help me, that's literally Emma Roberts, not Emma Watson," the fan tweeted, alongside a screenshot of a young Roberts wearing a pair of Minnie Mouse ears while eating breakfast, next to an identical screenshot from Roberts' Instagram feed.

Other "Harry Potter" fans quickly reacted to the mishap.

"Oh my god, HOW does this happen?" one person wrote with a crying emoji.

"All these Emmas look alike. Seriously, I can see making the mistake because this does look like it could be Emma [Watson]. What I don't get is not catching the mistake in quality control. Say letting the actors or some family member look at the kid pictures?" another asked.

"I literally thought of this while watching it!" another user commented. "I remember that photo making the rounds when they were filming ['Deathly Hallows'] pt 1 when Hermione uses obliviate on her parents and you see baby photos of Emma Watson. People were saying that this photo was 'exclusive' from the set."

Producers of the reunion special later confirmed that they used the wrong photo and promised to correct the mistake.

"Well spotted Harry Potter fans!" they said in a statement to Entertainment Weekly. "You brought an editing mistake of a mislabeled photograph to our attention. New version up shortly."

"Return to Hogwarts" marked the first time that most of the cast members had reunited on screen since the "Harry Potter" franchise wrapped filming. The first movie, "Harry Potter and the Sorcerer's Stone," premiered in 2001, and the franchise concluded a decade later with the release of the eighth film, "Harry Potter and the Deathly Hallows: Part 2."

Among the revelations in the reunion special was that Watson considered leaving the role of Hermione around the time the cast was set to film "Harry Potter and the Order of the Phoenix," the fifth movie in the series, according to People.

"The fame thing had finally hit home in a big way," Watson revealed, explaining that she felt a great deal of loneliness during that time.

Co-star Tom Felton noted that while he had his "cronies" and Daniel Radcliffe and Rupert Grint had each other to lean on during their rise to fame, Watson was "not only younger but she was by herself."

"People definitely forget what she took on and how gracefully she did it," Felton said of Watson's superstardom.

"Harry Potter 20th Anniversary: Return to Hogwarts" is now streaming on HBO Max.

Emma Roberts
Emma Roberts is pictured attending the Vanity Fair Oscar party at Wallis Annenberg Center for the Performing Arts in Beverly Hills California on Feb. 24, 2019. Dia Dipasupil/Getty Images