"↔️I guess after all those pranks over the years somebody decided to get their revenge," Oliver wrote on Instagram, showing a picture of himself and his twin brother, James Phelps, who played Fred Weasley, in the special with their names reversed on the screen. "It was fantastic to be part of the HP reunion. Hope you all enjoyed it. #ReturnToHogwarts."
Matthew Lewis, who played Neville Longbottom in the franchise, commented, "This is legit hilarious. Dude. Wtf? Haha."
But it was Tom Felton, who played the villainous Slytherin Draco Malfoy, who jokingly copped to the swap. "It was my doing :) #weaslebee #returntohogwarts 🐍 > 🦁," Felton remarked, using his character's nickname for Ron Weasley.
The reunion special marked the 20th anniversary of the release of Harry Potter and the Sorcerer's Stone, and began streaming New Year's Day on HBO Max.
Many of the series' original cast returned for the tribute, including the Phelps brothers, Felton, Lewis, Watson, Daniel Radcliffe (Harry Potter), and Rupert Grint (Ron Weasley).
For more from the reunion special, watch the video below.