"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 birthmark grows, and she even tries 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. When Nick's parents put Grace to bed, Nick gets up to go tickle her. A short while after, Grace says to Nick, "If you tickle me again kid, I'll rip your arm off!" As Nick flees, he hears her say, "I'll get rid of you creep. Just wait until I can walk!'"