Gary the Snail is SpongeBob's pet snail. Gary usually can only say, "Meow," while sea worms in the show bark, which indicates that snails are the ocean equivalent of cats and worms are dogs. In some episodes, Gary says things other than "meow" but this is unusual. Gary is the sixth or seventh main character of the show, he has the fifth most appearances in the Series.
In "Opposite Day," Gary tried to do the opposite of his stereotypes by barking like a dog.
In "The Secret Box," Gary responded to SpongeBob's question with "Meow-no". SpongeBob did not think much of it and replied, "Aww, what do you know? You're a snail!" SpongeBob did not recognize it as special, meaning this is not the first time Gary spoke. In the movie, The Citizens of Bikini Bottom were chanting, "All hail Plankton," while Gary chanted monotonously, "Meow, Plankton."
In many episodes, it has been indicated that Gary is very intelligent even being more intelligent than all the main characters (excluding Plankton), this is ironic as he is a snail, the biggest hint of which was in "Sleepy Time," where Gary spoke in his dream (that SpongeBob was interrupting) and sounded very old and wise.
He had an extensive library, which is a possible metaphor for intelligence. He is a domesticated house pet with similar mannerisms to a cat but also has royal blood as seen in "Rule of Dumb." Curiously, in Rule of Dumb, it proves that Gary and Patrick are cousins, as their fathers were brothers.
It is suggested that SpongeBob had Gary when he lived with his parents as a young boy. The episode "Treats!" reveals that Gary was adopted. As seen in "Gary Takes a Bath," Gary can levitate and teleport, possibly meaning that psychic powers run in the Star family, as Patrick has psychic abilities. Gary did not appear again after "Help Wanted" until the episodes "Plankton!" and "Naughty Nautical Neighbors." Gary has been to many places including the large Bass Vegas.
Gary had a minor role in the episode Atlantis SquarePantis. Gary appears wearing a party hat and blowing on a paper horn. Gary is also a very good musician, although he was not part of Squidward's band in the episode "Band Geeks." In "The Paper," he played Squidward's Clarinet very well, and Squidward had confusion. In "Procrastination," Gary played the trumpet. In "Something Smells," Gary played the violin to make SpongeBob cry while chopping onions because SpongeBob told him to.
Gary has the strange ability to become a floor buffer, as shown in Sentimental Sponge.
In "Patty Caper," when SpongeBob blames Gary for supposedly stealing the secret ingredient to the Krabby Patty, Gary describes another suspect—Squidward, and, based on the picture Patrick had drawn of him, Gary must think Squidward is very ugly.
In "Little Yellow Book," he bites Squidward's tentacle because he was saying horrible words.
In addition, "Your Shoe's Untied" reveals that Gary has feet.
Gary can say the words "Plankton," "Yeah!", and "No."
Also to illustrate Gary's antagonism towards Squidward, in "I Was a Teenage Gary," when SpongeBob answers the door, to Squidward, holding Gary, Gary hisses at him.
Gary has arms as seen in "Have You Seen This Snail?", "The Gift of Gum," and "Grooming Gary."
According to "Gary Takes a Bath," "Rock-a-Bye Bivalve," and "Pet Sitter Pat, Gary can read because in "Rock-a-Bye Bivalve," he is seen reading the newspaper, and in "Gary Takes a Bath," he is seen reading a book called "Snail Jokes". He was also reading a book called "Snail Tails" to Patrick at the end of "Pet Sitter Pat," although due to Gary's lack of English, Patrick could not understand him, as explained when he said "Snail Tails? I thought it was called 'Meow Meow Meow.'"
Gary has many things hidden under his shell: a house, SpongeBob's Krabby Patty T-shirt, a record player, a diamond, and many other pieces of junk.
In the episode "Treats!", SpongeBob says that Gary's full name is "Gerald Wilson Jr."
In the pilot episode "Help Wanted," Gary's pupils are small red dots and his meow is much squeakier.