Alonzo

Alonzo is a large black and white cat. He seems to be the kind who is friend with about everyone, and much like Rum Tum Tugger and Bombalurina, Alonzo is a very sensual cat.
Alonzo seems to like to keep to himself, but though he's often in the background he has a manner that attracts attention.
And he is there when needed, when Macavity took Demeter and Munkustrap was trying to stop him and get her back, Alonzo ran up and took her from both so that Macavity coulnd't harm her. He is kind of the second in command after Munkustrap.
And when Munkustrap was injured in the fight with Macavity Alonzo is there to take his place.
It seems like he has something for Cassandra, they could have and relation or the beginning on one.