Showing user-specific content

Is there a way to show specific users some specific content? I mean a manual selection, not something based on Roles.

In other words, as the site admin, I will manually create a new account for a user.
I will also create a Page that is specific to this user.
Example:
If John logs in, show him a link to a Page I wrote about dogs, because I know he likes them.
If Sarah logs in, show her a link a page I wrote about cats, because she likes cats.

So how can I link a specific page to a specific user? Ideally when making a new Page, I could select a username from a drop-down…