Deezil Oyl is Olive Oyl's little niece, who first appeared in the Popeye the Sailor episode "Popeye's Junior Headache" (1960). She looks like a miniature version of her aunt and wears a big bow in her hair. She has a bratty demeanor, particularly towards Popeye. In the online comic strip Popeye's Cartoon Club, it is revealed that her father is Castor Oyl, with her mother most likely being Cylinda Oyl.
- "Popeye is finished 'cause I ate the spinach for Popeye the Sailor Man haha!" (Popeye's Junior Headache)
- "Uncle Popeye, oh, please tell me a bedtime story, will ya please tell?, will ya? will ya? will ya?" (The Mark of Zero)
- "Good night, Uncle Popeye." (The Mark of Zero)
- To honor tradition with the Oyl family, her name is a pun on diesel oil.
- Olive has quadruplet nieces that are identical in appearance if not size. Deezil, a conceited brat, is one of them.
- Deezil's voice is provided by Mae Questel, who uses the same voice she uses for Swee'Pea.