This, ladies and gents, is the original idea Walt Disney had about Pluto, the dog.
He's really just a guy who wanted to help Mickey the Mouse, paid off his debts, and visited Micky's home. But Mickey didn't want Eustace (Pluto's real name) to leave because Eustace was Mickey's first friend, so Mickey took a rock, knocked Eustace out, and dressed him up like a dog to keep with him forever.
Yeah, you could understand why Walt did the smart thing and never aired THAT creepy shit again.
Above synopsis is brought to you by Creepypasta: The Shit Nightmares are Made Of.
summary: mickey met someone who he saw as a only friend. however, this 'friend' didnt want to be friends any more but mickey was afraid of losing another friend so he mutated him into pluto. thats also the reason why mickey risks his life to save pluto, so that people dont find out pluto isnt supposed to exist. its said to have been a halloween special made up by walt, he thought that children were dumbed down and that they were capable of watching stuff like mutations and operations