This is a difference from the book and movie. In the book Gus wants to watch V for Vendetta in the basement but his parents make them watch it upstairs in the living room and none of that happens in the movie
"You're like a millennial Natalie Portman. Like I'm V for Vendetta." (1.17). After Gus says this Hazel goes over and watches V for Vendetta with him. Him telling her this starts off their whole relationship. If he never said anything to her though, they probably would not have ever met or dated.