Grub was one of the prototype names for W.O.R.M.S.
(The Ultimate Guide to G.I. Joe 1982-1994: Identification and Price Guide - by Mark Bellomo)
As with the rest of the crew, I wanted a figure that would fit in with something from 1987. Hasbro has done repaints in the past, and some molds have even been repurposed from their original designs. The latter inspired this figure, which uses a mold from 1988: Armadillo.
The mold reminded me of a mechanic, which turned out to be the secondary role for this figure. I also tried to stay true the original W.O.R.M.S. color scheme. The legs had a lot of detail that was not originally painted, and I think it helps break up the brown.
The antenna is a reproduction from joereproparts.com.