Or you can spawn the Townie and NPC Maker from Insim and tell it to make a new batch of townies. Or downtownies. (Downtownies have more money.) They won't replace the ones you have; it will just add a whole new batch of about 50 new ones that you have never met before or sold anything to.
If you do make new townies, let me suggest you also temporarily install a set of default face replacements. Your new townies will get the default faces. You can remove the defaults package after you make the new townies (if you want), but the new townies will keep the new faces.
My own set is here:
http://sumomo.modthesims2.com/showthread.php?t=130190