In the book Holes who is Squid?

Squid is the nickname of one of the boys who has been sent to Camp Green Lake after being found guilty of committing a felony. He is one of the first two boys Mr. Pendanski introduces to Stanley Yelnats soon after Stanley's arrival (the other boy being Rex). Squid's real name is Alan but he, like the rest of Stanley's group in tent D, prefers his nickname.
Alan, Zigzag, and Stanley are the only three white boys in their group; the others are either black or Hispanic. Stanley does not notice, at first, that Alan (Squid) is white since both he and Rex are covered in dirt and don't look much different from one another. Alan is also the boy who Mr. Pendanski tells to go to the Rec Hall and bring the other boys to meet Stanley.
Squid is a reasonably active participant in Stanley's life at the camp. He is the one who affirms Stanley's new status as Caveman after Stanley gets involved in an altercation with another boy called Lump. He states:

The Caveman's one tough dude.

Squid is also the one who teases Stanley about writing letters to his mother and is the boy who Stanley hears crying one evening. Squid is embarrassed about being discovered in such a vulnerable condition. He tells Stanley that he has allergies and threatens him with violence if he should mention the incident.
Other than the fact that Squid is just as much involved in the daily routine of life at Camp Green Lake as everyone else, the facets mentioned above are the most significant aspects about him and his relationship with Stanley.