Instructions
Start a dog fight. These begin automatically when you reach certain plot-critical locations. Your first dog fight starts on Level 3, "A Bird Named Kevin," shortly after you pass the mushrooms. Other fights occur during Levels 6, 7 and 10.
Select which character you want to play as. The game presents you with a character selection menu when a dog ambush begins. Initially, your only choices are Mr. Fredricksen and Russel. After Level 6, you will also be able to play as Dug the Golden Retriever. To choose between them, use the direction pad and then select your choice with X button for the PlayStation 3 and the A button for the Xbox 360 and Wii.
Press the buttons on your controller when prompted. For instance, if the game prompts you to press the X button, press it. Your character will strike one of the dogs, knocking it unconscious. Repeat this with all the dogs.