Owner Michelle Olsson planned to take Jagger, the Staffordshire Bull Terrier, to the vet on Thursday after she noticed his back leg was swollen. 

She said she placed Jagger in the black Commodore, threw her car keys down on the seat and shut the door. 

"He has walked across the seat and stood on the keys, and locked the door," she said. 

"I could not believe it."  

Ms Olsson said it was the middle of the day, about 35 degrees but she did not panic.

"There was a plumber working across the road and he came over to help," she said. 

"We called the RACV but they said they were going to be an hour.

"The plumber, who was also a firefighter, gave me his phone to call the CFA." 

Ms Olsson said the plumber hosed the the car down with water while she waited for the CFA to arrive. 

She said she contemplated smashing in the car window in to retrieve Jagger. 

"The firies arrived and we were talking about what to do," she said. 

"Jagger walked across the seat again, stood on the keys and unlocked the car."

"It was amazing." 

Ms Olsson said Jagger was a character. 

Marong CFA volunteer Tim Scott said the incident was one of the most bizarre he had ever attended. 

"It was very funny to think a dog could manage to lock and unlock himself from a car," he said.