Daniel Radcliffe, Emma Watson and Rupert Grint Revisit Hogwarts in the ‘Harry Potter’ Reunion Trailer

“Think of a powerful memory. Make it the happiest you can remember.” They’re Daniel Radcliffe’s words, uttered in the opening moments of the trailer for Harry Potter 20th Anniversary: Return to Hogwarts — and, just like the title for this HBO reunion special, they say it all.

First announced…