Take your screaming twins into the store in their double stroller. Even better, make sure one screaming twin has a big cut under her eye.* Wonder if you are making things better or worse by saying things such as, "Mommy will be as fast as she can at the store!" and "I'm sorry you're upset; we'll be going home soon!" in a loud, falsely cheerful voice.
Slink out of store with head bowed and invisible tail between legs.
(I know all parents have had such moments and I know more are to come [The tantrums! I fear the tantrums!], but boy can people give you the judgmental glares when your kids are crying!)
*Um, yes, so OK, yesterday I was holding Maddie on my lap and trying to open a package by slitting the tape with a mechanical pencil. The mechanical pencil slipped and cut Maddie under the eye. Thank goodness it didn't oh, say, GOUGE HER EYE OUT, but still. I felt horrible. My first really big dumb mom moment.