[quote name='beerguy961']Were smurfs mammals or some kind of egg laying species?[/QUOTE]
Since no female smurfs existed before Gargamel created Smurfette, one has to assume that smurfs reproduce assexually. Since there is never any evidence or eggshells or such in the smurf village, I'd assume that when the patriarch Smurf wants to increase the population, he plants a mushroom (the housing for that smurf), and then somehow imparts some spore into that mushroom, which multiplies as the mushroom grows... so there is never a housing issue in the smurf village.
Because of the clearly defined roles in the community each smurf plays, some of the patriach smurf's thoughs must be imparted into the spores, as you don't see dupilation of many roles in the smurf society.
Gargamel, knowing this, scuplted a female smurf in clay, and then somehow synthesied the "Smurf Spores" to create Smurfette.