It's the format that's used as the video file for most common "cutscenes" like the intro video to Super Smash Bros Brawl. Someone once decribed it as being a collection of successive JPEG images played as a movie (similar to MJPEG AVI files but a different container format than AVI). Unfortunately I forgot the name of the file format. If someone knows the file format's name or file extension, please let me know. Thanks.