A Great Dane that belonged to James Kirk and had been dead for seven years by 2293, restored to him inside the Nexus in Star Trek Generations.
Butler is Kirk's dog, a large Great Dane, seen in Star Trek Generations.
When Kirk is swept out of the Enterprise-B and into the Nexus, he finds himself at the mountain house he once shared with Antonia. Butler bounds up to greet him as he chops wood, and Kirk is delighted and then puzzled, telling Picard that the dog has been dead for seven years and that he sold the house long ago.
The animal is one of the first clues, for Kirk and for the audience, that the Nexus is giving him back a past that no longer exists. Picard uses the same unreality to persuade him that the life on offer there, however pleasant, cannot make a difference to anyone.