While it's not my parents, I did get my Nana to watch Black Cat with me once, this was our conversation:
Me: Nana, I'm cosplaying this guy (Lin Xiao Li)
Nana: That's a guy?
Me: yes, that's a guy. A guy with a magical rainbow scarf of doom.
Nana: He's very Pretty, now who's the green haired guy?
Me: That's Sven.
Nana: Who's him in your group?
Nana: Don't smoke. It's bad for you.
Me: I know Nana, I have paper cigarettes.
Nana: Good. Now that's the guy your friend is cosplaying, right? That you made the gloves for?
Me: Yes Nana, that's Jenos.
Nana: And who's this lady?
Me: That's Echidna. She's Creed's Henchwoman.
Nana: Is anyone her in your group?
Me: I also agreed to be her.
Nana: She's pretty. Now which one's Creed again?
Me: The one with the really weird laugh.
Nana: Oh yeah, him.
Me: I'm gonna cosplay him as well.
Nana: ...you better wear something under that.
Working on:Yuu Kashima-Gekkan Shoujo Nozaki Kun, Namakelder-Happiness Charge Pretty Cure!, Henry Branwell-The Infernal Devices books, Drusilla-Buffy the Vampire Slayer, Carswell Thorne-The Lunar Chronicles, Woolsey Scott-The Infernal Devices books, Mad Hatter-Are You Alice, Cure Passion-Fresh Pretty Cure! Gilbert Nightray-Pandora Hearts, Monk-Ghost Hunt,