Snellie is a female sea snail that has a lavender shell with a purple swirl. She has a large pink bow tie on the top of her shell. Her eyes have blue irises with black pupils and long, girly eyelashes.
She appears in the episode "The Great Snail Race," where she races against Gary, and Patrick's rock. Squidward keeps Snellie away from Gary because of his hatred of Gary and SpongeBob. Gary is pushed too hard by SpongeBob and gets hurt badly.
Snellie goes back to him instead of finishing the race to see if he is okay. In the end, Gary and Snellie seem to have fallen in love with each other and go off the track together. Snellie and Gary tend to be partners, but she has not been shown with Gary in any other episodes. She possibly could have been donated by Squidward or is just a continuity error.
What makes it strange is that they look identical possibly meaning they're twins. Or they are possibly siblings.
Snellie's snail carrier is a collectible item in the game, SpongeBob's Truth or Square. When it is viewed in the hub, Snellie's eyes poke out, along with Snellie's meowing, before they see each other and go back into the carrier. In the DS version, Snellie herself replaces the item.
Her name may be derived from the Dutch word "Snel" which translates to "Fast" in English.