I don't know exactly who contributed to this mod, but it allows you to capture slaves during certain random encounters after a dialog check, and resell them to Metzger in the Den. Upon capturing a slave they will appear in your inventory, looking either like Tandi's or Butch Harris's talking head. Both characters appear in Fallout 1.
After looking through some .PRO files, it also seems you can capture ghouls including super mutants.
Their inventory pictures may be talking heads of Set, ghoul leader of Necropolis and Harry the super mutant guarding its Watershed.