It's kinda' lazy that its actually really easy to put these NPCs in the spawn menu, but Gmod hasn't added it for some reason. I've noticed that there are some fully-functional HLS entities in the game, which are not in the spawnmenu by default. Ichthyosaur not doing damage? Its a simple fix. I DID NOT CODE OR MAKE THE NPCS, SIMPLY JUST ADDED THEM TO THE SPAWN MENU.
NOTE: YOU NEED HALF-LIFE: SOURCE MOUNTED IN-ORDER TO USE THIS ADDON.
