Note: It's not necessarily an exhaustive list, but it should be very close to it. Also, it does not guarantee that a contestant advanced.
While the judges otherwise refrain from commenting after the performances during the showcase round, Katy Perry made an exception when she repeatedly compared Elliot Greer to Vincent Van Gogh, following his performance of an original song.
All 3 Judges:
Kezia Istonia (a.k.a. Lady K.)
Only Lionel Richie: