Shelly is Principal Tarian’s beloved pet turtle. She only appears in Season 3.
Shelly Cam is when Shelly walks around the Quads's school with a camera on her back. The result is a laugh track and images of rapidly moving feet.
The School Carnival
During the school carnival, Shelly finds blue cotton candy on the ground. She is attracted to this. The principal says "No, Shelly" and walks offset.