I’m not sure whether this is true in the canon; but in the Shine world, Alucard has a room with no doors. He keeps some private things in there – including, apparently, spare clothes.

Alucard: Come along. I’ll get it some clothing.

Seras: What is he?

Alucard: Nothing I’ve ever seen before.

Seras: What’s in his mind?

Alucard: Nothing. Not only is he innocent, he’s a complete blank.

It’s as if the mind has never been used, as if it’s…

Seras: Fresh out of the box?

Alucard: Precisely.