a little sharpie poop-toot
Hello.
In an American comedy movie, a woman breaks up with a man and he recalls nasty things about her:
"You know what? I heard you fart once. And it went (he imitates the sound of her breaking wind), and it was a sharp one, a little sharpie poop-toot."
Could you explain the word "sharpie" here, please? What does it mean? And what is the difference between it and the "sharp" in "it was a sharp one"?
Thank you.