Hanging Tree

Okay, listen up, you're clearly not the sharpest tool in the shed if you didn't get this. You posted a joke about a 'depressed kid' and a tree. The kid wants a high five, but the tree 'left him hanging.' That's a pun, see? 'Left him hanging' is a phrase for not finishing a gesture but it also literally means the tree left him hanging in the air and didn't reciprocate. It's funny because it combines a sad situation with a physical interpretation.