If you have one of their other charge cards, and consistently put a lot of purchases on it, you may get an invitation to apply for the Platinum card. (valuepenguin.com)
Just be careful not to lose them; I would also think twice before putting major purchases on them that I might have cause to return or want purchase protection on. (travelsort.com)
Someone with an open credit card account can authorize you to make purchases on it. (valuepenguin.com)