Annie.. the costa ships are mostly identical to carnival ships, but not Allegra, Carnival does not have any ships that small anymore.
This ship used to belong to Regency cruise lines...
But FYI, almost ALL cruise ships use the same engines and have engine room systems made by the same company, Wartsilla in Germany.
It isn't just Carnival ships; Norwegian Epic had a Wartsilla engine blow up just before the ship was set to make its inaugural cruise - set it back by two weeks.