Mr. Hippo will sound just like his UCN self: He sounds like an old man who rambles a lot, and speaks in a new York accent. He compares his life to salmon swimming upstream, and being trapped at a stage to life as being a fish getting eaten by a predator. He is very wise.
Try to get creative with Mr. Hippos story and try your best to make it sound like Joe Gaudet's voice for him. No voice effects are needed for him. But try to be in a quiet room while voicing him....I don't want to hear to much noise in the background.