She is a dark gray squid with light yellow eyes and black pupils. She wears a red plaid skirt.
Sheila's first appearance is in the episode "Squeaky Boots" where she is one of Pearl's friends at her birthday and when Pearl is talking about the new "Flipper Slippers" she can be seen wearing them. In "Squirrel Jokes" she can be seen with Henry-Bart in the audience of the "Komedy Krabs". in the episode "Squilliam Returns" she is one of Squilliam Fancyson's rich friends and she can be seen with her brother Sheldon. She is also a student of Mrs. Puff's Boating School and on the Good Noodle Board, she has one star. She can be seen eating at the Krusty Krab in "Fear of a Krabby Patty" on Day 3 of nonstop service. Sheila also appears in Traffic, the SpongeBob short in the background of the traffic. In "The Good Krabby Name" she seems to be one of the few Citizens that has never set foot in the Krusty Krab, even though she has been seen there before. When Mr. Krabs shows a picture of her and asks SpongeBob if he has seen her before, he says no. At the end of the episode, she is among a mob of citizens that fell off the highway when Patrick and SpongeBob try to get customers into the Krusty Krab. In "Tunnel of Glove," she believes that SpongeBob is Pearl's boyfriend.
Sheila appeared as a child in the episode "Friend or Foe." She was short and green. Sheila also had cotton candy and a blue skirt. She was seen when Plankton floated away, holding a balloon. Mr. Krabs is looking up in the air and you can see Sheila as a kid. Sheila is probably around 18, but oddly, she was alive when Mr. Krabs was a kid.
"Finally. A cool place for teens to just, you know, hang out."
Sheila appears to be a giant squid and is friends with Pearl, a sperm whale, which is ironic, since both creatures in real life have a predator/prey relationship.