Conversation so far:
Why is Groucho Marx known for the mustache?
His distinctive appearance, carried over from his days in vaudeville, included quirks such as an exaggerated stooped posture, spectacles, cigar, and a thick greasepaint mustache and eyebrows.
Was there a way that Groucho Marx curled his mustache?
his was drawn onto his lip with grease paint, containing no hairs or bristles. In later life he grew his own, real moustache.

Question: What about his eyebrows make them notable?
Self-contained rewrite: What about Groucho Marx's eyebrows make them notable?