Einstein (aka “Einie”) was Dr. Emmett Brown’s 1985 sheepdog and later the Brown family’s pet. Age in 1985: unknown, however he was fully developed and probably “middle aged” for a dog. Albert Einstein was the latest of Doc’s many pet canines named after notable scientists. So it was only natural he became the world’s first time traveler.
Since Einstein was Doc’s only buddy (except from Marty McFly and Jennifer Parker), Doc would not risk his friend’s safety. Doc made an automatic dog food feeder for Einstein. Also “friends” with Marty and a happy, friendly dog. He only ate canned food and was walked twice a day, as Doc noted in his letter to Marty. Doc’s liver snacks are also a hit.
Einstein was at Doc Brown’s first time travel experiment in the Twin Pines Mall parking lot. On October 26, 1985, at 1:20 a.m., Einstein left his DeLorean time machine and arrived at 1:21 a.m., with Doc piloting it remotely and Marty filming. Unharmed, Einstein stepped back into Doc’s van and was “totally ignorant that anything transpired.”
Minutes later, Einstein barked from the vehicle, warning Doc that the Libyan terrorists (from whom he received plutonium for the time machine) had arrived at the Mall. Einstein stayed in the truck after the terrorists killed Doc and trailed Marty around the parking lot until he vanished in 1955.
Marty may have warned Doc in 1955 of his fate in 1985. Doc wore a bulletproof vest and survived the terrorists in 1985. Doc transported Einstein into the future after returning Marty home. What transpired while they were there is unknown, although Doc left Einstein in a suspended animation kennel to pick up Marty in 1985. (and Jennifer, who happened to be there).