Wasn’t Mariah Carey named Godmother of the Fantasy? Why wouldn’t they have done a traditional christening?
IIRC, it had something to do with Mariah being in the lobby where the ceremony was. She didn't want to be out in the wind so Nick Cannon was the one who smashed the champagne while she was basically the MC in the Fantasy's atrium. The theory was that this went against cruising tradition and explains why the Fantasy has apparently had more mechanical issues than the other three
I'm not saying I believe that, but it's what I read. I've never been on the Fantasy so I can't speak from experience about what it's like. And unfortunately, I might be a while until I get a chance...