Hotpoint vented counter-saver microwave
green peppers jumping and sparking

It's possible there were small metallic particles in the peppers, from the
soil, harvesting equipment, processing machinery, or whatever. I had that
happen once or twice, but it's rare.

This also happens occasionally with paper towels that use recycled paper.
Little metal particles end up in the paper and spark like you mentioned. Of
course, paper is flammable, and this has been known to start fires in
microwaves. Though, in all honesty, I have never seen this happen myself.

Then I put in just a plain bowl of water and it
started steaming pretty fast too.

I'm not familiar with your microwave, but if you do not have a turntable I
would guess the system that distributes the microwaves has failed. This is
typically a rotating metal reflector, under a cover on the top side of the
microwave cavity that distributes the microwaves around the cavity. If it
stops turning the microwaves all get beamed into a single spot in the
microwave.

Try putting the water/food in a different location in the oven and see if
you get the same results. I'm guessing it'll cook differently, in which
case it's probably time to have the oven serviced. It's usually a fairly
simple repair, but you'll need to weigh the cost of the repair against the
cost of a new oven.

Anthony