Frog's Best Friend is the second half of the 12th episode of season 2 of Rocko's Modern Life.
Bev adopts Earl as her pet. Earl acts viciously to Ed but like a pussycat to Bev Bighead.
At Dr. HP Marten's Institute for Questionable Experiments, a fairly godmother frees Earl from a cage, feeling that he has learned his lesson from his vicious past. Following his freedom, Earl proceeds in promptly devouring his fairy godmother and escapes from the building. He heads to the city of O-Town.
At the Bigheads' house, Bev is offered flies from the Maggot Farms delivery guy. The delivery man then hears a loud growl in the bushes and slowly sneaks to his truck, where he finds Spunky at his ankles. When he reaches to pet him, he is bitten from behind by Earl. Back in the Bigheads' house, Bev tells Ed that the flies aren't for him since he is on a diet, and is offered a small amount of cottage cheese instead, much to Ed's annoyance. Bev gives Ed a bag to throw in the garbage on his way to the car to get to work. But when Ed does so, he finds that Earl has destroyed the Maggot Farms truck entirely. Ed runs away, with Earl chasing after him. He hops inside his car and drives away. But Earl manages to catch up and chews off the bumper. Earl decides to go to the Bigheads' yard and digs up the flowers. Bev comes outside and rebukes the vicious dog, who suddenly feels regretful when Bev orders him to put the flowers back. Bev also feel regretful for shouting at him and pets the now-gentle dog, who realizes that she is nice after sniffing her hand. Bev then notices a tag on his collar that says "Earl (Dog) Specimen" with the numbers 60295378. She becomes appalled of the fact that the dog has been attempted to be sold by scientists as an experiment and decides to adopt him.
Later that night, Ed returns home and finds the adopted dog cuddled under Bev. Ed apprehensively demands Bev to get rid of him, but Bev tells him that he is adopted and compels him to assist her or he will eat less than he is eating now. So Ed plays catch with Earl outside and the vicious dog ends up attacking him. During dinner, Bev feeds Earl a stack of steaks while Ed only gets a double of the small amount of cottage cheese. Later, Earl torments Ed by stuffing him inside a garbage can and giving him a bath.
Later, Bev suggests that Ed should take Earl out for a walk, but the grumpy toad refuses, until Bev offers him a steak to give to Earl, giving Ed an idea. When they walk outside, he tries to eat the steak for himself, but Earl snatches it away from him. Ed has finally had it and decides to get rid of Earl once and for all. He tricks Earl into getting into the back of a truck and drives to the landing center, where he leads Earl into a flying spaceship. When Ed returns home, Bev asks him what happened to Earl. Knowing that thare is no way for him out of this, Ed disguises himself as the dog in front of Bev. But she catches on when Earl returns to the Bigheads' house in a space shuttle. Knowing that he has no other option, Ed finally decides to call the pound. Eventually, Ed is caught by the dog catcher, who mistakes him for Earl since Ed still has the disguise on, and is sent to the pound, where the other dogs are offered steak. When Ed tries to shoo another dog away from a piece of steak he is about to eat, the dog shouts at him and eats the steak. Ed then ends his dialogue with his catchphrase "I hate my life."