The answer to this is probably no, but it is worth asking about just in case.
I was really tired and mistitled this. It should be Park Hopper partial refunds.
If I decide to buy a 3 day park hopper pass and only use it for a day, then something comes up and I decide I don't need the other 2 days on the hopper pass could I go to Disney customer service or wherever and refund the difference between a 3 day park hopper and a single day park hopper?
I could probably try selling my remaining 2 days on Ebay or something, but that's technically not legal according to Disneyland. Plus, I don't think I'll be wanting to scalp tickets on my honeymoon!