Justin Bieber
The 17-year-old American singer, who is touring Australia, told a crowd of screaming fans: "Everybody give it up for this kid."
"I just wanted to say, he is very inspirational, he shows other people to stand up for what they believe in," he added, before Casey introduced Bieber's next song Never Say Never.
Casey, 15, made headlines after turning the tables on a bully at his high school, body slamming him on to concrete.
The video of him hitting back went viral on the internet.
Bieber has one more show in Melbourne tonight night, before heading to Adelaide and Perth.
