But Tom Felton recently told us a secret about the first film, Harry Potter and the Philosopher's Stone, and it's left us seriously floored.
Speaking on an Instagram live, where he watched back segments of the movie with fans, the actor revealed that his granddad, Nigel Anstey, is actually in the movie as a background extra, and can be spotted on a number of occasions throughout.
Showing fans excitedly the moments he appeared, Tom pointed out his grandfather could be seen briefly at the staff table in the Great Hall, as Harry, Ron, Hermione and Malfoy enter for the first time.
When Professor Quirrell announces there's a troll in the dungeon, Tom's grandfather can be seen again.
"That's my gramps!", Tom excitedly declared after watching this moment. "Oh my days, it actually goes my gramps then me."
Anstey then crops up again during the first Quidditch match, sitting next to Lee Jordan.
When he isn't starring in Hazza P, Tom's granddad is actually a pretty established geophysicist, who even has an award named after him.
He should definitely add the world of film to his CV, though - if not for his own mini role then for the help he gave Draco star Tom to prepare for the part.
Speaking to the Hollywood Reporter back in 2011, Tom said his granddad actually helped him to work on his 'Draco snarl'.
"My grandfather did help me a bit with that...learning how to do it," he said. "It's sort of the signature Draco expression and Grands had me practice a lot.
"I got it down eventually. Everything got easier as the character developed".
As he watched back the first Harry Potter film in December, his gramps was just one of many observations.
"There I am in the background ... the little cocky sh*t," he joked at one point as he saw himself on screen.
When Harry snubs Malfoy's friendship offer early in the movie, Tom also had some choice thoughts.
"I'm not sure who I want to defend there," he said. "Screw you, Potter! But no, screw you, Malfoy. He's a real d*ck."
Tom took part in the watch along in order to raise money for the Best Friends Animal Society, bringing in over $3,000 (£2,197) by the end.
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