I am an excellent straight-ahead animator, yea verily. And of course, in keeping with previous posts, I will explain to you what straight ahead animation is.
Simply, straight ahead animation is when you animate, drawing one picture after another, without having any previous layouts to guide you. The opposite to straight ahead animation is key frame animation, where certain "key" poses, or important poses, are drawn first, and other drawings are created to fill in the gaps between the keys. These gap-fillers are, appropriately enough, entitled "inbetweens."
When do you use straight ahead animation? Mostly, you use it on flowing, erratic things like liquids and cloth, pushing through the pages of artwork with an immediate style and sense of motion. So why don't you use straight ahead animation all the time, if it's so immediate and flowy like some New Age music video? Because if you do, you'll run into problems - characters won't fit in with the layout properly, or end up moving out of frame, and often you'll have to go back and redo the work you've already slaved over.
I rejoice when it comes time for the straight ahead animation to be done - my cloth flows naturally, my liquids drip and quiver realistically, and I feel great when I'm actually sitting down and animating. I don't know why, but I get this tremendous rush when I'm freed of keyframes and layouts - perhaps my little hidden anarchist taking a peep between my animator's eyelids? Perhaps.
Back to work. Or maybe a nap. The white sheets on my bed beckon with greater urgency than the white sheafs of paper glaring from the light desk. If I get this film done in time for the UCLA Animation Prom, someone else has been animating my film.