Johnny was the name of a Great Dane that Lester Dent owned. Johnny made a posthumous appearance in the August 1945 Doc Savage story titled “The Wee Ones.”

Mr. And Mrs. Dent Home From Trip East – The article states the Dents have returned after a two month visit in New York where Dent was renewing contracts with Street & Smith for the Doc Savage Magazine. Dent talks about defense contracts and the European war. He also remarks that his Great Dane, Johnny, has inspired a new story.
Source: La Plata Home Press (La Plata, Missouri), Thursday, April 17, 1941

Johnny Poisoned – Dent’s Great Dane, Johnny, was poisoned and died. The article noted that several other dogs in the area had also been poisoned.
Source: La Plata Home Press (La Plata, Missouri), Thursday, November 4, 1943 – Page 1

Johnny, Dent’s dog, originally belonged to another author who started in the pulps. Steve Fisher and Frank Gruber both knew Dent when they were young aspiring writers struggling to survive on the pulp market in New York City. Gruber notes that Fisher became more successful and bought a Great Dane which he took everywhere he went. The dog traveled with Fisher to France and Hollywood. Returning to New York City, Fisher ran into trouble with a hotel manager and was told to get rid of the animal. Gruber states that Dent liked Johnny and offered him $50. Dent was moving back to Missouri and Johnny went with Dent. Gruber tells the story of Fisher calling Dent from Hollywood and asking to have Johnny bark into the phone.
Source: The Pulp Jungle by Frank Gruber, page 35, Sherbourne Press, Inc., 1967