Besides Cisco's Harry Potter reference in season 2 episode 20 in The Flash, the actor Tom Felton who plays Julian Albert AKA Dr. Alchemy was also in the Harry Potter movies as Draco Malfoy. In the spin-off from the Harry Potter franchise, Fantastic Beasts And Where To Find Them had Ezra Miller play as Credence Barebone who will also being playing the Flash in his own movie along with other DC superheroes in Justice League Part 1, and any other DC movies. This is wild and awesome!
As we all know by now, J.K. Rowling maintains an active presence on Twitter, and apparently keeps an eye on her old Harry Potter actors (see her priceless reaction to Matthew Lewis' shirtless photos back in May). Today, she gave her seal of approval to a series of friendly ribbings between Lewis (who played Neville Longbottom) and Tom Felton (who played Draco Malfoy).