Daniel Radcliffe, Emma Watson and Rupert Grint reunite and reminisce in the full trailer for HBO Max's Harry Potter 20th Anniversary: Return to Hogwarts special -- which also teases Helena Bonham Carter donning her Belletrix teeth and more familiar faces including Ralph Fiennes, Tom Felton, Matthew lewis, Bonnie Wright, Gary Oldman and more. The special premieres New Year's Day.
