Poirot and Hastings are adorable in this book:
Poirot looked at me and sighed.
"If only - if only, Hastings, you would part your hair in the middle instead of the side! What a difference it would make to the symmetry of your appearance. And your moustache. If you must have a moustache, let it be a real moustache - a thing of beauty, such as mine."
Repressing a shudder at the thought, I took the note firmly from Poirot´s hand and left the room.
And I´m a big fan of Poirot´s moustache:
We have been slowly ascending the zig-zag path up the cliff. It was at this juncture that we passed throught the little gate into the grounds of End House.
"Pouf!" said Poirot. "That ascent is a steep one. I am hot. My moustaches are limp. [...]"