Answer:
Toby (the golden retriever)
(Keep in mind after he was rescued after the heatstroke he was renamed to be called "Bailey" so if the questions asks for more here it is)
Explanation:
If you remember there's a scene where Toby opens the knob and goes out into real world. There a truck driver picks him up and drives towards a bar. Toby is left alone in the car while the driver goes to the bar. The, Toby begins suffering from heat exhaustion in the cab.
