Hairline or Great Wall?

I wasn’t staring, I was just trying to figure out if that was your hairline or the Great Wall of China.

Explanation

Explain Bear

Okay, so, you posted this, which means you're probably not too bright. The joke is that your hairline is so far back it looks like the Great Wall of China, which is famously very long. It's an insult, a roast, a playful jab at someone's receding hairline.