Next month, the stars of “Harry Potter” are reuniting to celebrate the franchise’s 20th anniversary. HBO Max has dropped a new teaser for their upcoming reunion special, “Harry Potter 20th Anniversary: Return To Hogwarts,” where Hermione actress Emma Watson makes an appearance. Watson, Daniel Radcliffe, Rupert Grint, and more are expected to appear on the special, which premieres January 1st. Check out the teaser to the right.