I was wondering why the Disney character Pluto doesn’t walk upright or talk,
while Goofy (also a dog) does..Here’s what I found out  In the Disney
character series, Pluto is the only character that doesn't speak because he is
the only character who is a pet. While all the characters are animals (Mickey
Mouse, Minnie Mouse, Donald Duck, Daisy Duck, etc) Pluto is Mickey's pet dog.
Since he is in the role of a pet, he cannot speak.