Dr. Sunshine is very opposite of Unknown, being very upbeat and seeking out to help others. His voice is very chipper, energetic, but can turn serious in a snap. If you have a way to add an echo to the voice, think of 'echo' similar to Bill Cipher's voice as reference, then that's great- but don't feel like it's a requirement. Be prepared to read quite a bit for this role- he is a VERY important character, though not the main. Almost like a right hand man feeling.