Spinach can also make it black.

blood, usually. or excessive iron in the diet.

Did he eat oreos?

Black can indicate blood in the stomach

My pediatrician said it could happen if the child is constipated, but if it keeps happening, take them in as it could be a sign of internal bleeding.

He ate banana today as well but he's eaten them before and this never happened.

Every time any of my girls are bananas their poop was black. It was so weird. I never could figure out why.

He didn't eat anything out of the ordinary except I gave him grape juice today but that's all. I usually water his juice down but today I didn't. Could that have caused it though? It's really black. Like charcoal smeared on his diaper. I've never seen that before. I took a pic but I didn't post it because I know nobody wants to see that. Lol

Or she got ahold of one of your iron pills. Is it actually possible to eat so much natural iron that your poop is black?

Did she eat anything with food coloring?? Or a lot of blueberries / blackberries?