Muffet is the Underturn version of Flowey.
She initially acts friendly and polite, and calls herself "Your best friend". She uses Southern Jargon at the end of her sentences, such as " Howdy" or "Golly". When she drops the charade, she often calls the protagonist an "idiot". She is malevolent and cruel, and berates the protagonist for not following her "Kill or Be Killed" philosophy.
During the Genocide run, after exhausting the RUINs kill counter and killing Scora, she recognizes the protagonist as Papyrus. At the end, she is afraid, and even kills Grillby in a vain attempt to save her own life.
She has a lavender androecium, 6 dark purple petals, purple eyes and a green stem and green leaves.