From WENN.com

Helena Bonham Carter, who played witch Bellatrix Lestrange, is among the cast members who stepped back into costume to film additional footage at the Potter studios in Hertfordshire, England.

A source tells Britain's The Sun, ""The cast have really enjoyed getting back together - they are so tight-knit.

""The shooting schedule is nowhere near as long as the films, so though filming has been intense, the stars have enjoyed being able to pop in and out.""

The film will be displayed at the The Wizarding World of Harry Potter attraction in Florida, as well as two new theme parks under construction in California and Japan.