"Strained Peas" is the third short story in the book Tales to Give You Goosebumps.
Nicholas Morgan is reading a comic book called Iron Man: The Mark of Dr. Destro. Then his mother arrives home from the hospital with the baby, Hannah. Strange things start to happen around her. Her eyes change color, her heart-shaped birth mark grows, and she even wants to kill him! He comes to believe that Hannah is a monster, despite his parents' assurances that there is a perfectly normal explanation for everything.
Eventually it is discovered that while in the hospital, Hannah was accidentally switched at birth with the boy's real sister, and she is not related to him at all. She is returned to the hospital. The boy seems pleased with the real baby, Grace - until she begins talking in an evil voice and commands him to stop the baby talk and bring her some food. Hearing this, Nicholas realizes that this baby may be worse than the last and sighs in exhaustion.