He’s a bit of a gobshite. He struggles to keep his sarcasm under lock and key and when he’s found someone who he can bounce his wit off, he finds himself in his element.
Up until he meets Thatch, he doesn’t believe he’s built for relationships. He had a pretty violent and harsh childhood growing up under the tyrannical rule of his alpha father.
Callen uses humour as a defence mechanism. Having been hurt so much and having no choice to break free from his pack in Northern Queensland, it would have been easy for him to be bitter and spiral out of control. Instead, he focused on being the best he could be in the Supernatural Investigation & Crime Bureau. And in doing so, faced backlash from not only from his father’s pack, but agents too due to his father’s reputation. Humour became his amour to deflect the blows.
Callen struggles with authority. Sometimes his arrogance can piss off the powers that be. He rides the line, barely… just enough so his doesn’t get himself fired. Thatch is the first “boss” who he follows with only the occasional grumble. Though, he does like it when Thatch becomes growly.
Callen is renowned for his unusual interrogation techniques. ABBA and slime have been known to be effective. You’ll just have to read Thicker Than Water to get a better idea of how.