She is a subtle parody of Cher (whose real name is Cherilyn Sarkasian). Sonny and Cher were animated in the New Scooby-Doo Movies in the 1970s, however that episode has never been released because of legal disputes. So instead of using the animated version of Cher in this series (like Don Knotts and Mama Cass Elliot) they created a youth obsessed, raven haired woman with emaciated arms and deep affectless voice.

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Sheila Altoonian is a friend of Nan Blake's. She is very jealous of Nan's good looks, so she steals ingredient from all over, to make a youth potion.

Scooby-Doo! Mystery Incorporated

Although Sheila was supposed to be one of Nan Blake's friends, she was secretly jealous of her more youthful appearance while hers were giving way to time. Aging gracefully not being an option she dressed up as a vampire to steal things for her youth potion. This led to suspicion by Mystery Inc. and Sheriff Bronson Stone that Nan might be the vampire. When it came to the climax at a local museum, they trapped the vampire. When Daphne was about to stake it, the vampire gave up, revealing herself to be Sheila who wanted the stolen items to create a youth potion to regain her beauty. Sheila was eventually arrested by Sheriff Stone. (The Secret Serum)