Sponge Ball routines were just about the first things I learned. I still love them!
I'm also a very big fan of those "special" surprise finish sponges. The self working kind like "Caught Red Handed" where you push a spongeball into your empty closed fist and open the hand to reveal that the ball has been replaced with a huge red sponge hand, or puppy, or dragon, or whatever....

I recently purchased a Sponge "Ding-Dong" expecting it to be the same type of device. Much to my disappointment, it was not a self working effect, but rather a rather large sponge "Ding-Dong" with instructions on how to fold it to look like 3 sponge balls which you are supposed to switch for the 3 actual sponge balls that lastly appeared in your victim's... er... Spectator's hand for the grand finale...

I guess I have 2 questions...

1. Is there a manufacturer that makes a device of this nature that transforms from a ball like the Red Hand?

and/or

2. Is there a way to learn how to create your own devices of this nature?

1) Not to my knowledge.

2) Try Viagra.
Actually, if you look at the bunny / red hand / whatever, you could take a pair of scissors and try to duplicate the gaff in your . . . that is, in the SPONGE . . . er . . . item . . . then, like the old joke about Michelangelo, just cut away everything that doesn't look like a sponge ball.

Good luck. I think.

Honus,
I've thought about that... I've also thought about taking the one I have and cutting a domed hole in the base to see If it could be inverted into a ball shape..

I was hoping to find someone in the Café with some experience in manufacturing invertable sponge shapes...