My son noticed that the battery area of our TV remote was quite hot. I
immediately removed the batteries, both were almost too hot to hold
onto. Sorry, I didn't check to see if the batteries were installed
with the polarities correct. They had gotten so hot that the plastic
surrounding the negative terminal that connects to the PCB was
slightly melted and deformed.

A new set of batteries did not cause the remote to function.

I disassembled the remote and completely cleaned it. Scraped gunk out
of the holes in the remote casing with a small jewelers screwdriver
followed with a toothbrush and soapy water. Cleaned the flexible
plastic sheet that functions as the button pad with soapy water and
toothbrush. Completely dried everything with a hair dryer. Carefully
pulled on spring for neg. terminal, stretching it so it will retain a
battery, reassembled and put in fresh set of batteries. All is well.

What caused the batteries to get hot?