For some reason I thought the Perry's did those ugly plastic Catachans.
I don't know if it's on EVERY
GW box, but somewhere on the box it'll probably have who sculpted it. On the two boxes I have sitting next to me here, it's next to where the "Citadel" and "Games Workshop" labels and copyright/trademark details are located.
The regular plastic Cadians are sculpted by Brian Nelson.
Yeah, have a look at the text the the left of the barcode on this catachan box....
http://www.spacemarines.co.uk/warhammer/warhammer40k/boxContentsImages/imperialGuardCatachanJungleFighters/boxBack.JPG Says it's "Designed by: Michael Perry, Alan Perry and Jes Goodwin"