The Farmer is a man who Elfo found early on during his journey. When he was asked for his name, he said they were humble people without names, but said that Elfo may call him Farmer.
Farmer's Wife believes her food is flavorless and brings no joy. Elfo believes otherwise and says he only ever had candy up to this point. The farmers then thought of him as a king until he dismissed their claims.
Once Elfo started praising him and his wife, the two became defensive, Farmer saying he was far too humble to receive praise, believing he should instead be beaten with his food.
After further compliments, they became hostile, telling him he has gone too far and must leave. The Farmer's Wife called him Praiser, which may be a derogatory slur or it might have been a spur-of-the-moment title given to him.
It is unknown why they acted this way, or when Elfo left, why they told him he was ruining their lives. It is possible they have been indirectly brainwashed or are naturally submissive.
Season three episode eight: "Hey, Pig Spender"
A monster knocks on her door, later it turns out that it is human-merkimer and attacks the farmers. They ask to stop because they are just humble farmers. Later you can see the farmer storming into the thronsal and announcing that a monster is coming to get them all.