He talks trash like crazy. An opponent once accused KG of calling him a "cancer patient."
Source: ESPN
This quote from teammate Jason Collins: "He could be telling you about the weather, and he’ll break out in a full sweat. His intensity is just non-stop."
Source: BS Report
He gives completely unhinged postgame interviews, like when he declared a game against Orlando a "bar fight."
He once got into a fight with teammate Wally Szczerbiak because he criticized him during practice.
Source: CBC
He once started sprinting back-and-forth during a practice when he was supposed to be resting.
Source: ESPN
He mentally destroyed Carmelo Anthony in a game, leading to Melo confronting him in the parking lot.
Source: TMZ