My husband and I saw a lady on Mariner of the Seas with a tiny dog she pushed in a special stroller. She took it into the buffet and everything.
There are licensed emotional companion dogs here in Ca. They can't be denied even to live in Apartments without pets. You have to have a doctor fill out the application to get one.
When I worked in the Cruise terminal in San Francisco years ago, We used to work the Old Regal Princess 10 day turn around for Alaska and Mexico. One sailing to Alaska the ship welcomed 200 blind guests and their dogs. It was an amazing thing to witness. They brought a huge roll of sod and laid it on the top deck so the dogs could play and use the bathroom in comfort, Yes there were other cruise guests on board who were not part of the party, but they all said they had a spectacular cruise, the dogs were wonderfully behaved of course, and it was said they all had a fantastic time as well.