From GMod Wiki
In the Game Menu, the NPC Menu brings up a selection of all the Non Player Characters (NPCs) which you can create. Friend or enemy NPCs can be created from this menu. Click on one and it is immediately created at the place where the crosshair was when the Game Menu was opened.
- You can add more NPCs to be spawned in this menu through addons.
- You can add more weapons that NPCs can be spawned with through addons.
- NPC spawn icons are not automatically generated. A pre-made texture must be made and assigned manually.
- Overflowing the NPC Weapon list with custom content makes the now off-screen weapons completely unselectable.
- Downloading a reskin for an NPC will make it appear in pink and black squares.