Gleeson played the evil Joffrey Baratheon in the hit television show before the character met his demise in season four.
Eagle-eyed fans spotted Gleeson, who looks unrecognisable from his Thrones character, in the news season as Dodgy Mo, a friend of Sean, the brother of Maeve Wiley (Emma Mackey).
One fan wrote of the appearance, “Joffrey, what are you doing here?” while another added, “what’s Joffrey doing in sex education?!” See more of the fan reaction here:
You can see some more of the fan reaction to Gleeson’s appearance here:
Sex Education is officially coming to an end now with its fourth season.
Created by Laurie Nunn, the Netflix show’s final season picks up as Otis (Asa Butterfield) and Eric (Ncuti Gatwa) face setting up a new sex clinic at Cavendish Sixth Form College.
New cast additions for the final season include Schitt’s Creek star Dan Levy, Thaddea Graham, Lisa McGrillis, Marie Reuther, Jodie Turner-Smith and Eshaan Akbar.
NME’s four star review of the final season said: “Thankfully, the show finds its warm and witty rhythm when the writers return to their regular M.O. – exploring awkward aspects of sex and sexuality in a way that no other show seems capable of…farewell, Sex Education, and thanks for the messy memories.”
Sex Education is available to stream on Netflix now.