[Stinged]

The best way (speed and difficulty) to do this is by using either MySQL or SQLite.

You can create 2 tables, one of them contains the "main" name and its "PG?" name, and the other one contains data for the "PG" name you select.

Table 1:

Username	Name
Alex_Palermitano	Aaron_Smith
Alex_Palermitano	Jake_Jeffords
Alex_Palermitano	Walter_Black

Table 2:

Name	Level
Walter_Black	5

Or you can have them all in one table.
Which one is better depends on how you want to do stuff.
For example, if 3 names are necessary, then one table is better. If they're not, it's better to have another table than to have some fields that will not be used.