Sakuga (作画) (lit., “drawing pictures”) “is a term used in anime to describe moments in a show or movie when the quality of the animation improves drastically, typically for the sake of making a dramatic point or enlivening the action”.
I’ve been watching anime for over a decade now and anyone that has watched several anime must have noticed the difference between animation. Sakuga animation in many is the highest level of Japanese animation. Generally most anime is made with animation limitation. The limits usually comes in the form of skipped frames or the animation of characters mouth’s during conversation. Sakuga animation in contrast is fluid and full of expression. Sakuga animation is often reserved for important battles scenes in anime, due to time constraints and expense. There are two primary types of sakuga animation. Genga which means “key frame animation”. Douga is the second form of sakuga, it means “ In between drawing”. I would recommend watching “Sakuga: The Animation of Anime” on YouTube for further explanation.
YouTube features a host of AMV depicting sakuga animation check them out.
Some helpful blog post: