here is how you do it with cookie cutters: these can be applied to media generators to have a solid color, or to a video to have video in them...
Vertical:
Horizontal:
to make them fatter/skinnier adjust the square size. you can also adjust the border size/color, how much feathering you want, etc.
play around with the effect its somewhat fun
as for making them move that depends on how you want them to move, one easy way is to cut the image into clips and use the yellow square in it to move it into different places on the different clips, this will make them jump, but to do it with keyframes i believe you just right click on the keyframe and choose "hold" and it will hold till the next keyframe..
otherwise use the keyframes on leniar and they will slide to the places you want them (for example the one i used in the beginning of walking in the butterflies)