Well, your dream is kind of self-explanatory. Your little rodent friend is thought of as a second class citizen by the dog, or by your sister. I wonder what the guinea pig had to say? One nice thing is that at least he has a name, Charles, while the dog is just a nameless chihuahua! Charles lets you have a piece of his mind about it was considered to be a rodent, which is lower on the evolutionary scale than a mammal, like a dog. Your dream is not weird. It is kind of cute or humorous to imagine. It is as if these two animals think they are people, and almost start a fight about it. I really don't think there is any hidden meaning in this dream. There may be some tension between you and your sister though, and the tension is shown through this standoff with these two animals.