It's just part of the inspection routine to inspect the insides of toilet tanks. Typical findings include plumes of rust and corrosion on the tank bolts or some type of a jerry-rigged link between a flushing handle and a flapper.
While in the home stretch on this inspection, which was clean vacant home, I found this little guy or girl. Which sex it was I'm not qualified to determine. This GA gray tree frog did not move a muscle. I hope the new owners leave him alone. The little cut-out in the back of the tank allows it to come and go with the lid on.
If you happen to need a home inspector in GA, don't hesitate to contact me directly.