The Stevensons are a couple that appeared in "A Fish out of Water". After Peter Griffin takes out a loan with his house as collateral, the bank then sells the house along with everything in it to the Stevensons. Peter then eventually raises money to buy the house back. At the end of the episode, they are seen in bed with Peter and Lois.
Jim Stevenson is a very cultured man. In a game of Pictionary, Stewie is angered by his inability to play the game as evidence by repeating "Jackal" eight times.
Abby Stevenson is Jim's wife. It is very apparent that she has some appreciation of art. She treats Peter like if he was her own son.