The Cleveland Cavaliers thought it would be cute to come out to the Monstars' anthem to start game 3. It's a little hard to hear in the video but if you listen closely you can make it out:
This likely stemmed from a combination of Isaiah Thomas' comments before game 2 about the Cavs, "they're not the Monstars", aligned with the similarities between the 1st half of Friday night's massacre in Boston and the Toons vs Monstars game in Space Jam:
So the Cavs decided to have a little fun at the Celtics expense.