I love this kind of documentary. This is because it's always fun to watch the cast and crew talk about their experiences filming a particular movie and working with their co-stars as well as the crew of that particular movie.
This is the longest of the four featurettes on the DVD of The Mask, with a running time of about 27 minutes. It consists of interviews(most of them new), behind the scenes footage, clips of the film and frames from the comic books.