Melmo was given a bottle of candy from God. The blue candy turns Melmo into a lovely 19-year-old version of herself, while the red candy turns her back into a child. Combining the two turns her first into a fetus, then into an animal of her choosing. When Melmo ages from 9 to 19 her clothes don't grow with her, usually resulting either in shredded clothes, or skin-tight children's clothes on the body of an adult woman.

Melmo is a kind-hearted young girl who is frequently torn between her actual age and the things she encounters and wants as her older self.

The 19-year-old Melmo is quite beautiful and men frequently fall in love with her.