It's learned that Hayley had a twin named Baily, and this is the only time we see him. Yet in an earlier episode it's learned that Hayley was born in Africa and didn't have a twin.
Roger says he visits Dana Plato's grave. Dana Plato doesn't have a grave, she was cremated
During Francine's old stand-up act she stated that her adoptive parents are Chinese and at family reunions, due to her superior height, they all yell 'Godzilla'. Godzilla is a Japanese creature.