While heading to Violet City Ash and friends encounter a baby Stantler, who got separated from its herd. Brock manages to take care of the Stantler but the herd appears and attacks Ash and Co. Turns out that Stantler have been terrorizing the town, but it was an illusion created by the baby to protect itself. Later, the baby appears and takes a liking to Brock. What will Brock do when the baby's real mother appears?
Brock had to be cruel to the baby Stantler so it can be with its herd, because Brock knew that was what was best for it when the family arrived. It is very uncommon for a Pokémon breeder to do this.
Although the title refers to the baby Stantler's Pokemon species, The Little Big Horn is a river in the mid-west USA, which was the site of a famous battle between General Custer of the US Army and several Native American tribes led by Sitting Bull in 1876.