One has a well and septic system. After returning from a long weekend away there was a frog sitting in the toilet bowl of the downstairs bathroom.How would the frog have gotten into the toilet?

The frog is that prince of a fellow your wife is having an affair with. She must have let him stay there for the weekend. Upon your return, your wife, being a woman, needed to run to the bathroom first, before you. When she got to the bathroom, there he was. So she kissed him. One of those special kisses, the ones that turn adulterous fellows into frogs. Then she tossed him in the toilet, which she was just about to flush when you walked in. You saved the dear fellow. Drive him to a pond far, far away. Or have him neutered and keep him in a jar next to the bed.