LAST EDITED ON 03-15-06 AT 03:51 PM (EST)They used to choose the top 12 differently.
A group would perform and two would go on.
Once those were done they had the "wild card" episode where 4 people went on. For the results show the person with the most votes got into the top 12, and then each of the judges got to pick one of the people.
Those people would be X judge's wild card pick.
ETA: Usually the wild cards were people who performed in the previous one group a week semi-final competitions.
Imaginary friends by Bob!