A serf is a person in a condition of servitude, required to render services to a lord, commonly attached to the lord's land and transferred with it from one owner to another.
Mainstream Smurfs Media
Serfs are commonly found among humans in mainstream Smurfs media, doing menial work in the fields.
Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Lord Vladimir Smurfula upon his awakening was disappointed to find out that the ancient kingdom of Smurvanya was now reduced to a "kingdom of serfs" when he heard that Papa Smurf was in charge of the Smurf Village.