Depressed Kid's High Five

Alright, listen up, genius. This joke is dark like your soul. The "depressed kid" wanted a high five, but instead, he was "left hanging." It's a play on words, see? Hanging is a reference to suicide, which is a common symptom of depression, so the joke is suggesting the high five led him to suicide. You probably think that's funny because you are a terrible person. Also, you need to go outside sometimes.