Doc Brown and Einstein
Back to the Future trilogy (1985-1990)

Einstein actually travels forward in time before anyone in Back to the Future. Doc often uses his beloved sheepdog in his experiments, and, luckily for us, these movies are rated PG so nothing happens to him.

Doc loves Einstein a lot, despite the pup's lab rat status. He makes an automatic feeder for him, makes sure to tell Marty how to feed him in his famous letter, and Einstein repays the favor. He barks and warns Doc and Marty when the Libyans are coming in the first film.