In the film, A Scanner Darkly, a technique called interpolated rotoscoping, or commonly referred to as just rotoscoping. In this method of filing and animation, a scene is filmed normally and then an animator then traces over the lines and animates the scene. Rotoscoping laid the groundwork for most blue and green screen work, most notably in Stars Wars Episodes 4-6. The rotoscoping was used to animate the lightsabers.
In the scene that I have posted below, Barris (Robert Downey Jr.) barges into house to exclaim pride over the new bike he has just acquired. While he is perfectly fine at acting, I believe that the use of rotoscoping here gives the scene more action and emotion. The animator is able to exaggerate certain features and the seemingly constant motion of the people makes the scene all that funnier.
One part in particular happens near the end when the discussion of asking someone about the bike and the missing gears. Woody Harrelson’s character gets up and spouts off about fighting the guys who sold the bike to Barris and how they cheated him. The animation here gives Woody a larger than life personality. He looks like he is ready for anything. Also he is probably high on Substance D, a drug frequently taken in this movie.
I personally like this technique and feel it can help to get more out of an actor or actress than is physically in the realm of live action.