Character mistake: At one point in the show, Roger throws a bucket of water (in disguise as Scotch Bingeington) on Francine claiming "Wet T-Shirt Contest!" Francine looks disgusted when Roger states "Eh, give this one a four" to the guy judging the contest, then says to Francine "Don't feel bad, you've had three kids." Francine replies "I've had two." and Roger gasps and puts a consoling hand on Francine's shoulder. This is wrong because Francine has birthed four children. She previously gave birth to Bailey (Hayley's twin), and Greg and Terry's baby in Season 3 Episode 7 "Surro-Gate." (00:14:15)
The 42-Year-Old Virgin - S3-E6
Continuity mistake: This episode reveals Stan has never killed anyone, even though he killed Jay Leno in Stan of Arabia: Part 1, killed Jackson's Double in It's Good To Be Queen, accidentally disintegrates one of his co-workers in I Can't Stan You, and shot a hang glider in An Apocalypse to Remember.
Tearjerker - S3-E10
Character mistake: When Tearjerker is describing his evil plot to Stan, he says he auditioned for a role in Monster's Ball in 2002. Monster's Ball was released in 2001.
Chosen answer: It is just the decision of the creators to do so.
MasterOfAll