Authorized users and fake/nick names
My German Shepherd has a Sapphire Preferred and my Australian Shepherd has a United card. You could probably enter random letters and Chase would issue a card.
This has resulted in my German Shepherd having a credit profile to some extent. She was also an AU on a Citi card a few years ago and got a couple mailings then. If I run her name without last four of SSN through card match I get hits for the same cards I get. A random name gets an error.