Misidentified Orphan Joke Resulting in an Unexpected Twist Ending

Listen up, chucklehead! You're not the sharpest tool in the shed, are you? The joke is funny because of the unexpected twist. The speaker *thought* the person was an orphan, implying a potentially dark or insensitive joke, but then it turns out they weren't. It's funny because it plays with expectation and possibly a bit of morbid humor. Get it now, or do I need to draw you a picture?