In the beginning, when Debra informs Ray that both of her parents will come, she tells Ray that Marie said that Lois can stay at "your house", which would mean that Lois will stay at Ray's (and Debra's) house. What she actually should say is that Lois can stay at "her house", meaning that Lois would stay with Marie and Frank, which was the case.
Robert Culp's character name is "Warren". However, towards the end of the episode Ray refers to him by his real life name of "Bob".
When Warren and Lois stay at Ray's house for Thanksgiving, Lois sneaks over from Ray's parents' house for some extramarital sex. Ray accidentally walks in on them and later remarks that he saw "an arm and a foot and a little bit of Bob" thus referring to Debra's father by his real name instead of his character "Warren."
Actually, Ray says that he saw "an arm and a foot and a little bit of bottom", not "Bob" (although he kind of mumbles it, so it is easy to mishear it). Therefore, this is not actually a goof.