I forgot to cut the bananas before putting them in the fridge, what should I do?

Bread knife works great on frozen bananas.

I agree with Suzanne, and actually it's okay if they've softened a tiny bit before going in the food processor, as long as they're still mostly frozen.

If you have a really sharp knife you should be able to cut the frozen banana's, if not you could let them thaw a little, cut and put back in the freezer for a while until they are frozen solid again.