When Peter and the guys try to salvage a sunken Mercedes-Benz, Peter half-heartedly promises a favor to a helpful dolphin named Billy Finn (guest voice Ricky Gervais).

When Billy shows up at Peter's door looking for a place to stay after his wife throws him out, he reluctantly lets him stay.
After a few days, Peter finally tires of his new house guest & tries to reunite Billy with his wife.

Meanwhile Stewie tells Brian about his abusive nursery school teacher but Brian is reluctant to take action when she turns out to be someone he wants to date.