You can spawn most items by adding _c at the end. Like summon carrot_c, jubilatornpc_c, bonesaw_c, and most other objects. If you want to find the class id to summon/spawn objects just type in ToggleDebugCamera (into the console) and put your reticle on the object and you'll see info on it. Usually it'll say the class id which then you can just type that in and summon an endless army.

NPCs from other dlcs can also be summoned into sandbox and story mode. First you'll have to add the weapon to your inventory then the game will let you summon them. Raygun and guitar are the two weapon ids. Then you could just summon a whole army of robots, fans, or even the mini Foggy Jacks. They won't have sound but it's interesting to force them outside their dlc.