Create squishy (jelly) collision looks. How do I start?

I have this pong like game. When the ball collides with the wall, I want the ball to look like this:

Do you see how the ball sorta combines with the ball, and as it flies away, the ball separates from the wall? I want a similar, jelly like effect. This is for mobile. I can use a sprite or mesh, either is fine. How would I go about doing this?

 

I would suggest using a mesh. Use a bunch of small rigidbody with colliders on them. Join them together with springs. Then build a mesh on top that uses the colliders as vertices. I used a similar concept to produce the water physics in Pond Wars.