Hmmm. Either real or comic-book style Hippos have a very strong symbolic element to them. First, as you know they lurk under water so what might that symbolize to you when you reread your dream? Secondly, they are very aggressive.
Remember that everything in a dream is symbolic of some element of you and your life. The question is how can you apply a lurking, aggressive, maternal image to your life, either past or present? Think about that and then think about your cousin too. Another way to look at this dream is to be the Mama Hippo. What, if anything, did you or your male cousin door want to do? What line did he drop (symbolically) that pissed momma off? It could be something you thought of as a joke (pink cartoon hippos), something like harmless flirting perhaps? Cousins often test their sexuality on each other with little or no harm doe but sometimes deeper feelings, forbidden feelings, get stirred up. Your dream feels that way to Dream Momma.
What to do? Well, best thing is to own it, if only to yourself. Then poof, it's gone just like the Wicked Witch of the West. Got red (or pink) shoes? Put 'em on, click three times, then find a distant cousin to flirt with.
To answer your last question, yes, and no. Dreams do not come from the imagination, they are reality based and come from your unconscious, and therefore they are meaningful.
Dream Momma is a certified Jungian depth-psychotherapist with 20 years experience working with dreams. She can be reached at [email protected]