What are the shoes called that actually have a spherical ball underneath the sole of the shoe?

Baker: What are the shoes called that actually have a spherical ball underneath the sole of the shoe?
So I was on the Texas Tech University campus the other day, and I saw someone gliding around on these shoes, but each of them had about a 4-inch in diameter spherical ball underneath them. NOT to be confused with skate shoes or anything of the sort. What are these things!?

Answers and Views:

Answer by whatever1152
hmmm not sure all ive herd of were some weird skethcers thing and heelys

Answer by Butter
Heelies!!!!