Sheila is a bluish-gray female squid of Bikini Bottom with a red plaid skirt.
Her first appearance was in the episode Squeaky Boots where she is one of Pearl's friends at her birthday and when Pearl was talking about the new "Flipper Slippers" she can be seen wearing them. In Squirrel Jokes she 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. Shelia also appears in Traffic, the SpongeBob short in the background of the traffic. In The Good Krabby Name she seemed to be one of the few Citizens that have never set foot in the Krusty Krab, even though she has been seen there before. When Mr. Krabs showed a picture of her and asked SpongeBob if he had seen her before he said 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. She is different from Squidward though they're both cephalopods. However, she is a squid, whereas Squidward is confirmed to be an octopus.
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Shelia appeared as a child in the episode "Friend or Foe". She was short and green. Shelia 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 Shelia as a kid. Shelia is probably around 18, but oddly, she was alive when Mr. Krabs was a kid.