Squidward thinks Sandy is the only normal person in his environment. As seen in episode "Squidtastic Voyage," Sandy actually cares about him and is very worried about him having swallowed his clarinet.
At the Krusty Krab Halloween party, Sandy greets Squidward, and he asks her what she is supposed to be. She answers, but he says "I don't get it." Sandy walks away offended, but Squidward does not seem to care.
Sandy attends Squidward's "funeral" along with many other "mourners."
Everyone, even Squidward, all wants Sandy to stay in Bikini Bottom. When Sandy says "Home is where you're surrounded by critters that care about ya" and everyone gathers around her, showing that even Squidward cares about her.
When Squidward apologizes to SpongeBob near the end of the episode, he says he also likes "Mr Krabs, Gary, Patrick, Sandy" and at the end of the episode, SpongeBob and everyone says "April Fools!" to Squidward. Spongebob says "What would we do without Squidward?" and they all smile at him.
Squidward says to Sandy "He's not in my thoughts" and Sandy replies "Well, think again." Additionally, Squidward helps Sandy find SpongeBob.
Squidward jokes with others about Sandy's pride that she is a land creature. He does however seem to apologize when Sandy rescues them from a seagull.
Season 4 is where their friendship develops from very occasional talking to something more. Sandy and Squidward both seem to care more about each other.
Sandy is seen visting Squidward at the hospital with Spongebob, Patrick, Mr. Krabs, and Patrick when he broke his laugh box.
Squidward begs Sandy to separate SpongeBob and himself, so she tries to help by creating a device.
Sandy seems to care most about Squidward in this episode, as she expresses a lot of concern towards him getting his clarinet stuck in his throat. They are laughing with each other and Sandy tries to gently calm him down.
Sandy goes to Squidward's clarinet recital.
Sandy calls Squidward "Squid Cakes."
Sandy says "You did it!" and touches his back.
Sandy and Squidward talk to each other in the Krusty Krab. She also says to let her friends go to a ghost as talking about Squidward, Mr. Krabs, and Patrick.
Sandy tries to help teach Squidward karate.
Squidward and Sandy play Patrick's game. Sandy gets mad at Squidward for making fun of Patrick's game.
Sandy helps him and the other Bikini Bottomites regain their intelligence back.
She, Squidward, Patrick, Plankton, and Mr. Krabs team up to help SpongeBob get rid of his Mocking Mimicry Madness.
When Squidward invents a new sport in order to kill Patrick and SpongeBob, Sandy shows up and sees through his intentions. In order to teach him a lesson, she challenges him for the sake of SpongeBob and Patrick, which she eventually wins.
Sandy is seen carrying Squidward away from the bicycles and skaters when he is almost crushed. Squidward also jumps on top on Sandy's head and is seen riding on Sandy's back.