Depressed Kid and Tree High-Five Fail: A Hanging Situation

Listen here, dummy. The joke is that the kid is depressed, and when he tried to high-five the tree, the tree didn't reciprocate, "leaving him hanging." This is funny because it's a play on words. "Left hanging" can mean both physically being left with your hand in the air and being abandoned or unsupported, which relates to the kid's depression. It's like, the tree is as emotionally unavailable as his parents. Get it now, genius?