Here's some info on the characters from Dog's Life.
Jake
He is the main character in this game, and he's a dog on a mission. A mission to save Daisy. Jake was born in Clarksville and has lived there all his life. He never strays from the Farmhouse much, and so not many people know his name. He also has a feature called Smellovision that can only be used by him, and also knows a lot of Doggy Do moves that other dogs don't know.
After Daisy was dog Napped, he fell out the truck and so he didn't see where the van went. That's why he set out on a journey across the states to find her. He may not be the toughest dog around, especially when he starts to loose health, but he's definitely one of the kindest as he will never do the opposite of what you say.