There are a lot of actors in Game of Thrones, but most of the actors are British actors, and most of these actors have participated in Harry Potter.
01. Michelle Fairley
In the film Adaptation Potter, Michelle Fellley plays Hermione's mother, Monica Wilkins, who appears in a scene where Hermione casts a Forgetting Curse on her parents before Hermione, Harry, and Ron go to find the Horcrux. And in Game of Thrones she plays Caitlin Tully, Mrs. Stark of the Wolf Family, Ned's wife, and the woman Littlefinger loves.
02. Freddie Steumar
Freddie Strawma, who starred in Harry Potter as Comyck McLagan, was a gryffindor student at Hogwarts School of Witchcraft and Wizardry, a senior than Harry Potter. In Game of Thrones, Freddie Stopma plays Deacon Tully, the younger brother of Jon's friend Sam Tully, but I don't know if it's out of date, and the actor is changed.
03. Seren Sid
In Game of Thrones, Ceren Sid plays the Night's Watch who betrays his oath and defects to the "King of Cyprus" Mance Red who defects outside the Great Wall, and he has a great influence among the wildlings. In Harry Potter, he played Albus Dumbledore, the younger brother of Albus Dumbledore. He made his debut in Harry Potter and the Order of the Phoenix, but his relationship with Dumbledore has been poor.
04. David Bradley
David Bradley played Argus Filch in Harry Potter, the gatekeeper of Hogwarts. However, his temper is very bad, which makes the students very annoying, and he especially likes to fight against the students. In Game of Thrones, he plays Wadefrey, the planner of the "Blood Wedding", and is also a repulsive character.
05. Natalie Turner
Natalie Turner played Aurony Fadora Tonks in Harry Potter, where she could easily change her hair color, appearance, etc., and was a member of the Order of the Phoenix. In Game of Thrones, she plays the Savage Osha, who is eventually killed by Little Peel.
painted eggshell
Frank Tierney, the young Voldemort in Harry Potter, is the son of Stephen Dylan, who played Stannis Baratheon in Game of Thrones.