say what?

It's been a long week in our household. Amelia has another ear infection and is not sleeping at night. This is in turn makes me very grumpy. I need at least 6 hours sleep or I turn into a grump. Wednesday she slept through the night so I thought yesterday would be a good day to tackle some errands. As soon as we got inside the store I realized it was not going to go well. Amelia was screeching and trying to escape the shopping cart. I was only there to get one thing so I headed directly to the shelf loaded up and headed to the register. Aiden is asking for something and Amelia is continuing her squawking arching her back routine which I'm ignoring. I overhear another customer at the other register make a comment about "...the Walmart baby". I could feel my face getting hot and myself getting mad. Granted she is screaming and has snot running down her face but really that's rude. She makes the comment again to the other cashier ( I think the cashier ignored the offensive comment the first time) and I look up and make eye contact with her. I have no idea how I am going to handle this because my kids are with me, I'm sleep deprived, etc. She makes the comment about the (cute) Walmart baby one more time and I realize in my frazzled states she's saying Hallmark baby. What's a Hallmark baby? I have no idea but it's nowhere near a Walmart baby, right?