Scale Bounce Expression
Here is a super cool expression to make your layer bounce like jello or gelatin.

timeToStart = .5; 
if (time > timeToStart) {
maxDev = 30; // max deviation in pixels
spd = 30; //speed of oscillation
decay = 1.0; //how fast it slows down
t = time - inPoint;
x = scale[0] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
y = scale[0]*scale[1]/x;
[x,y]
}
 else { 
value; 
}