Foammaker
Betz White has a tutorial on how to make a Super Foam-erator from a recycled plastic water bottle.
Betz writes:

In my quest for summer activities to entertain the boys I started reminiscing about a foam making toy I had as a kid. It was sort of shaped like a big plastic lolly pop with terry cloth on one side. You dunked it in water, put a little bubble soap on it and then blew into a tube. It didn’t make regular soap bubbles, it made long foamy snakes. I remember how much I played with that thing and knew my boys would enjoy a toy like that.