Jumper is introduced in chapter one of the book "Old Yeller" by Fred Gipson. Jumper is the family mule. He is described as being a dun mule that has a habit of escaping from fenced in areas. In fact, that is how Jumper got the name "Jumper." Papa named him "Jumper" because of his ability to jump over whatever fence was put up around him.
"Papa had named him Jumper because nobody yet had ever built a fence he couldn’t jump over."
Papa even exaggerated a bit and claimed that Jumper could even jump over the moon. Jumper is also described as being a fairly well behaved and hard working mule. He is calm to ride and carries his fair share of the work. About the only thing that Jumper has a bad habit of doing is quitting at the end of the day before he is told it is quitting time.
"Only, sometimes when I plowed him and he decided quitting time had come, he’d stop work right then."