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.
NEW[]
After looking through some .PRO files, it also seems you can capture ghouls including super mutants.
Unconfirmed[]
Their inventory pictures may be talking heads of Set, ghoul leader of Necropolis and Harry the super mutant guarding its Watershed.