Did Gary Coleman ever play stymie on the little rascals?

Absolutely not! The original films and shorts were filmed at least 20-40 years before Gary was born, and the "remake" had Kevin Jamal Woods as Stymie.

The original Stymie was played by Matthew Beard. Kevin Jamal Woods played Stymie in the Little Rascals remake.

However, Coleman was to have played Stymie in a proposed Little Rascals TV remake the Norman Lear produced around 1977.