On your most recent animation, of the one line bouncing around, once it starts slowing down the pacing and emphasis really reminds me of how I used to animate bouncing. Makes me want to buy Adobe Flash or whatever they call it now and get back into animating.
Anyway, I'm curious to know if you understand what you did, and why it works, in the couple of bounces where the line hangs in the air instead of following straight through. By creating that unrealistic pause in the air, it generates a sensation that "this moment is key" or "this moment is important" in some degree, and with the line bouncing around the walls, the slow to a near stop (I think you had 2 frames where the end of the line didn't move from the peak of the bounce) makes it incredibly clear that the ball is at the end of its lifespan, or the line is finishing its crazy, sporadic bouncing.
Whereas the transition from a normal line falling into high-speed chaos is created with the little bounce pad (nice particle effects on it disappearing, by the way), the transition from the line bouncing in near-straight lines at a ridiculous rate back to a regular bounce (and thus to an eventual end of motion) becomes pivotal around those 2 frames of hang time. The line could have kept bouncing away, always having an almost identical bounce up to bounce down, and the line would eventually reach its end, but by having that one moment where the line pauses at the peak, to then regain a bunch of speed and head back down into more bouncing, makes the animation feel dynamic, and the line feel alive. It adds a certain quality to it that makes the whole piece enjoyable to watch.
This is a good use of anticipation and exaggeration. If you want more research/reading material, here you go:
I highly recommend getting your hands on The Illustration of Life: Disney Animation.
If you'd like some videos that help teach and show this, here's a few videos.
