A couple things you can almost count on with greys. 1. They will get stuck on a sound or phrase that you don't like. 2. They will not say the things you want them to say. Just don't react in any way when your bird says the phrase you want to get rid of and he'll eventually get tired of it and move on to the next favourite.
Alfie doesn't want to know me until he has demolished all of his boxes
Perhaps I should start getting creative and make something like this as well to give him a bit of variety in what he has to shred!