GMod NPC Sticky This addon for Garry's Mod allows you to "stick" or weld NPCs to moving objects. If an object moves, the "stuck" NPC will move along with it, maintaining its relative position.

This will make all of the NPCs in Garry's Mod 'colorable'. What I mean by that is this will make certain parts of the NPC's model colorable while leaving other parts of them the original color.