Baby Stop is where a pregnant Stewie has Brian take him to shop for baby clothes when he makes himself pregnant by using Brian's DNA in "Stewie Is Enceinte".
After admiring the tiny clothes, Stewie asks a woman about her pregnancy. She questions his age and he snaps back about her looking about 40 and suggests that her fetus will likely be brain damaged. Brian quickly pulls Stewie away as he notes that he hated her.