Carter mixes up the words for "potato" and "tomato." He knows the difference between them, but will usually call them both a tomato until we correct him. I think it's easier for him to pronounce "tomato" so he just uses that one most often. Because when he says "potato", he really enunciates it slowly. "Poe. Tay. Toe."
Last week we went on a field trip to see Toy Story 3 on Ice and I was listening to him tell my mom all about it on the phone. When he said, "And we saw the tomato heads..." I couldn't stop laughing.