the Tree Witch was a one-time villain from the popular cartoon series, Adventure Time, a hideous old crone who lived in the forest she was a largely comical villain but did pose considerable threat due to her various magical powers.
When the Tree Witch first met Finn and Jake she overhead a bird calling them heroes, instantly wishing them to help her obtain princess hair in order to make herself beautiful (and cover her own balding) - yet when Finn tries to explain to the Witch they only help people in danger she captures Jake and sits on him, cursing him in the process and demands Finn get her the princess hair.
Left with no option Finn goes to extreme lengths to obtain princess hair for the Witch, ultimately managing to obtain some from Princess Bubblegum - however when the Witch is presented with the hair she is not impressed as it was literally bubblegum.
This caused Finn to finally lash out, confronting the Witch on her ugliness - not just on the outside but on the inside and that even with princess hair she would remain "ugly" (due to her evil nature) : this surprisingly makes the Witch relent and she frees Jake, seeming to be depressed at the realization Finn was right.
Finn, feeling sad for the Witch (despite her previous misdeeds) gives her his own hair after she notes she just wanted "beautiful" hair - yet shortly after obtaining Finn's hair the Witch decrees she will use her new hair for evil, she receives instant karma as she trips on her long hair, making Finn and Jake laugh.