About 7 years ago, Jerry fell asleep on and woke up to his dog, Kiko, finishing up snacking on his toe. Jerry had an infection that wasn't healing and the dog, out of natural instinct, took care of the problem.
So, Jerry woke up and his big toe was missing and his dog's face was all bloody. Turns out that Jerry had diabetes and didn't know it. That is the reason why his injury to his toe had not been healing. Jerry doesn't like doctors, despite being married to a nurse, and refused to get his toe checked out until that fateful day that Kiko made his move.
It turns out that Kiko saved Jerry's foot, and perhaps even his life. If the infection continued without being treated, who knows what would have happened.